FIELD OF THE DISCLOSED TECHNIQUE

The disclosed technique relates to waterless solar panel cleaning, in general, and to improved methods and systems for cleaning solar panels waterlessly using a robot, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE

Increased energy needs worldwide, along with increased demands for green energy have led to a rise in solar array parks worldwide. Solar arrays are arrangements of solar panels, usually in a linear or matrix form (i.e., rows upon rows), for collecting UV rays from sunlight and converting the received energy into electricity. Solar arrays in general come in two forms, either fixed angle or variable angle, which are also known as solar trackers since they can change their angle to track the movement of the sun over the sky during daylight hours. Industrial sized solar array parks have been set up across the globe, both in arid climates as well as wetter and more humid climates.

The energy efficiency of solar panels is directly correlated with the level of absorption of UV rays into the solar cells of each solar panel, itself correlated with the amount of soiling of the outer surface of the solar panels facing the sun. Soiling can come in the form of dust, dirt, debris, animal droppings as well as snow, ice, slush and other physical impediments on the solar panel surfaces. As solar panel energy efficiency is still far from 100%, the amount of soiling on solar panel surfaces in a solar park can seriously affect the efficiency and profitability of the solar park. Traditional methods for cleaning solar panel surfaces have involved human labor using hoses, wipers, cleaning rags and other similar equipment to keep solar panel surfaces free from soiling. Such methods, especially when used in solar parks that may have thousands of solar panels, are usually time consuming, expensive (due to the physical labor costs) and possibly wasteful from an energy perspective, as water (itself a natural energy source) must be used in copious quantities to properly clean solar panel surfaces. There is also the risk of human mistakes during manual cleaning which might cause damage to the solar panels, such as cracks in outer solar panel surface.

The past decade has seen a rise in automated solutions for cleaning solar panel surfaces, usually using a robot of sorts to clean the solar panel surface automatically. Some of these solutions involve the use of robots having nozzles, which spray a cleaning liquid onto the surface of the solar panels, and wipers which then wipe the cleaning liquid and any debris or dirt off of the solar panel surfaces. Recent advances in automated solutions for cleaning solar panel surfaces have shown that for most solar panel surface soiling, liquids are not needed to remove the soiling agent and most soiled solar panel surfaces can be cleaned with brushes or elements which wipe down solar panel surfaces waterlessly (i.e., without any liquid cleaning agent). Companies involved in developing such solutions include Ecoppia, Boson Robotics, Kashgar Sol-Bright, SunGrow and Air Touch Solar, to name a few.

Reference is now made to Figures 1A and 1 B, generally referenced 10 and 40 respectively, which are schematic illustrations of the prior art. Figure 1A shows a solar array 11 which includes a plurality of solar panels 12. As can be seen, solar panels are usually arranged in rows, each row having a height or width (as shown by a line 13). Shown in Figure 1 A is one configuration in which each row has a height of two solar panels, however other configurations are possible to increase the height of each row. As standard industrial solar panels can typically range in height from 1 -2 meters, height 13 of a solar panel row can typically range anywhere between 2-10 meters. Figure 1A also shows a schematic cleaning robot 14 of the prior art having an outer frame 18 surrounding a cleaning element 20 housed inside outer frame 18. As shown, cleaning robot 14 may be the height of a solar row and substantially travels longitudinally along the length of the solar row, shown by an arrow 16. As cleaning robot 14 travels in the direction of arrow 16, cleaning element 20 cleans the surface of the plurality of solar panels 12. The nature of cleaning element 20 in the prior art is further elaborated below in Figure 1 B.

Figure 1 B shows four different types of prior art cleaning elements for use as cleaning element 20 (Figure 1A), labeled using Roman numerals l-IV. In a first type of cleaning element (I), cleaning element 20 is embodied as a rotating cylinder 42, with the direction of rotation shown by an arrow 44 (clockwise in this case). Rotating cylinder 42 includes a plurality of brushes, or bristles, 46. Rotating cylinder 42 is encased in an outer frame (not shown) and positioned therein so that when rotating cylinder 42 rotates in the direction of arrow 44, plurality of brushes 46 comes into contact with a solar panel surface (not shown). The friction and brushing movement of plurality of brushes 46 sweeps any dirt, dust or debris as rotating cylinder 42 travels along the length of a solar row, eventually brushing the dirt or debris off the surface of the solar row. Examples of such a rotating cylinder are shown in US patent no. 9,831 ,820 B1 to Wang et al., entitled “Moving Mechanism and Photovoltaic Panel Cleaning Equipment Having Same” as well as Chinese patent application publication no. 209406900 U to Ting et al., entitled “Photovoltaic Panel Dust Removal Robot Capable of Crossing Obstacles Autonomously”.

In a second type of cleaning element (II), cleaning element 20 (Figure 1A) is embodied as a base 50 from which a plurality of bristles, combs, wipers or flaps 52 extends. Base 50 is located within an outer frame (not shown) and is positioned therein such that the extremities of plurality of bristles 52, shown by an arrow 54, come into contact and touch a solar panel surface (not shown). The contact of plurality of bristles 52 wipes and pushes any dirt, dust or debris forward as base 50 travels along the length of a solar row, eventually brushing the dirt or debris off the surface of the solar row, similar to the first type of cleaning element (I). In the case of the second type of cleaning element (II), base 50 does not rotate but merely travels forward with the movement of the outer frame. An example of such a base with a plurality of bristles is also shown in US patent no. 9,831 ,820 B1 to Wang et al., entitled “Moving Mechanism and Photovoltaic Panel Cleaning Equipment Having Same”. The patent to Wang contemplates the possibility of using both a rotating cylinder and a plurality of bristles.

In a third type of cleaning element (III), cleaning element 20 (Figure 1A) is embodied as a base 60 from which a plurality of nozzle heads 62 extends. Each nozzle head 62 can spray either a cleaning liquid or compressed air, schematically shown as a spray 64. In one version of such a cleaning element, as base 60 travels along the length of a solar row (not shown), spray 64 as compressed air is used to move the dirt or debris off the surface of the solar row, similar to the first type of cleaning element (I). In another version of such a cleaning element, as base 60 travels along the length of a solar row, spray 64 as a cleaning liquid is sprayed onto the solar panel surface. This may be followed by a wiper element (not shown), similar to the second type of cleaning element (II), which wipes the cleaning liquid and any dirt and debris off the surface of the solar panels. In the case of the second type of cleaning element (II), base 60 does not rotate but merely travels forward with the movement of the outer frame. An example of such a base with a plurality of nozzle heads is also shown in US patent no. 9,831 ,820 B1 to Wang et al., entitled “Moving Mechanism and Photovoltaic Panel Cleaning Equipment Having Same”. The patent to Wang also contemplates the possibility of using both a plurality of nozzle heads and a plurality of wipers.

In a fourth type of cleaning element (IV), cleaning element 20 is embodied as a rotating cylinder 70, with the direction of rotation shown by an arrow 72 (clockwise in this case). Rotating cylinder 70 includes a plurality of fins or elements 76, coupled with rotating cylinder 70 via a respective plurality of connectors 74. Rotating cylinder 70 and plurality of fins 76 are encased in an outer frame (not shown) and positioned therein so that when rotating cylinder 70 rotates in the direction of arrow 72, plurality of fins 76 comes into contact with a solar panel surface (not shown). The friction and touch of plurality of fins 76 sweeps any dirt, dust or debris as rotating cylinder 70 travels along the length of a solar row, eventually sweeping the dirt or debris off the surface of the solar row. Examples of such a rotating cylinder are shown in Chinese patent application publication no. 107309230 to Yiling, entitled “Automatic Cleaning Device of Photovoltaic Module”, US patent application publication no. 2015/0272413 A1 to Miyake et la., entitled “Autonomous-Travel Cleaning Robot” and US patent application publication no. 2019/0214940 A1 to Allouche et al., entitled “Method and Apparatus for Cleaning Surfaces”.

Whereas the prior art provides for waterless robotic solar panel cleaning solutions, the prior art nevertheless exhibits a number of limitations. One limitation is that due to the construction of cleaning element 20 (Figure 1A), as described and shown in Figure 1 B, which either brushes and/or sweeps and/or wipes dirt and debris horizontally along the length of a solar panel surface as shown in Figure 1A, the soiling may need to be swept relatively long distances before it reaches a place where is can fall to the ground off the surface of the solar panels. Solar rows may be hundreds of meters long, divided up into sections of solar panels stretching anywhere between 10-100 meters per section. Each section may be separated from an adjacent section by a small gap where some dirt and debris may be brushed off of the solar panel surface, however some dirt and debris may be moved over a significant length of a solar row before being swept off to the ground. Since cleaning element 20 travels horizontally, soiling may need to travel 10-50 meters (or even longer) before being brushed off the solar panel surface. In the case of fixed angle solar panels, where the angle of the solar panels relative to the ground may be only a few degrees, most of the soiling is moved horizontally and accumulates as cleaning element 20 moves over the solar panel surface. The accumulation of soiling as cleaning element 20 moves over the solar panel surfaces can cause damage to the solar panel surfaces. In addition, since copious amounts of dirt and debris may need to be moved over tens of meters before coming to a place where a significant amount of the dirt and debris can fall to the ground, the cleaning of such prior art solar panel cleaning robots may be inefficient and multiple passes of the cleaning element may be required to amply remove the soiling on the solar panel surface, thus leading to increased energy needs for cleaning solar panels. In addition, as solar panel arrays are usually angled, certainly in the case of fixed angle solar arrays, dirt and debris on the higher end of the solar panels of the solar array which is swept and/or brushed forward may travel slightly downwards (although not necessarily off the surface of the solar panels) due to the force of gravity as it is swept and/or brushed forward, thereby increasing the amount of soiling on the lower end of the solar panels of the solar array. The increased amount of soiling on the lower end of the solar panels of the solar array may thus necessitate multiple passes of any of the robotic solar panel cleaning systems of the prior art over the entire row of solar panels to substantially remove all the soiling on the solar panel surfaces. A further limitation is that the cleaning of the solar panel surfaces in some of the prior art may only be unidirectional depending on the design of the cleaning element. Unidirectional cleaning, for example in the case of a cleaning element including a plurality of nozzle heads and a plurality of wipers, necessitates a solar panel cleaning robot to return to its initial cleaning position at a given end of a solar row before going over the solar row a second time to further remove soiling on the solar panel surface not removed during the first pass of the solar panel cleaning robot. A further limitation is due to the size and weight of the solar panel cleaning robots of the prior art which include both an outer frame and a cleaning element for cleaning solar panel surfaces. Any added weight to a solar panel cleaning robot increases the chances that the cleaning robot may cause damage to the solar panels and solar panel surfaces as it moves over the solar panels horizontally.

What is needed is a waterless solar panel cleaning robot with increased cleaning efficiency thereby minimizing the number of passes required of the cleaning robot for amply removing soiling on the solar panel surface. What is also needed is a waterless solar panel cleaning robot capable of bidirectional cleaning. What is further needed is an efficient waterless solar panel cleaning robot having minimal weight even when the cleaning robot has a size substantially as large as the height of a solar panel row, in order to reduce the risk of damage to the solar panels due to the weight of the cleaning robot.

SUMMARY OF THE DISCLOSED TECHNIQUE

It is an object of the disclosed technique to provide a novel method and system for a frameless waterless solar panel robotic cleaner. In accordance with an aspect of the disclosed technique there is thus provided a frameless waterless solar panel robotic cleaner for cleaning at least one solar panel, including an upper element and a lower element, at least two coupling joints, a cleaning cylinder, at least one rechargeable power source, at least one drive motor, a rotation motor, a processor and a receiver. Each of the upper element and the lower element has at least two horizontal wheels and at least two vertical wheels, with a first one of the coupling joints being coupled with the upper element and a second one of the coupling joints being coupled with the lower element. The drive motor is coupled with the rechargeable power source. The cleaning cylinder is coupled between the upper element and the lower element via the coupling joints. The cleaning cylinder has a length substantially similar to the height of the solar panel and includes an internal cylinder, an external cylinder, a plurality of fasteners and at least one microfiber element. The internal cylinder is coupled with the coupling joints, the external cylinder surrounds the internal cylinder, the fasteners are positioned along the external cylinder and the microfiber element is coupled to the external cylinder via the fasteners. The rotation motor is coupled with the rechargeable power source and with the external cylinder and is for rotating the external cylinder and the microfiber element. The processor is coupled with the drive motor and the rotation motor and the transceiver is coupled with the processor. The drive motor is coupled with at least one of the horizontal wheels and the vertical wheels and is for driving at least one of the horizontal wheels and the vertical wheels. The plurality of fasteners are positioned along the external cylinder to give the microfiber element a helix shape along a length of the external cylinder. The coupling joints each respectively give the upper element and the lower element at least one degree of freedom.

In accordance with another aspect of the disclosed technique there is thus provided a frameless waterless solar panel robotic cleaner for cleaning at least one solar panel, including an upper element and a lower element, at least one profile, a cleaning cylinder, at least one rechargeable power source, at least one drive motor, a rotation motor, a processor and a receiver. Each of the upper element and the lower element has at least two horizontal wheels and at least two vertical wheels, with the profile for coupling between the upper element and the lower element. The drive motor is coupled with the rechargeable power source. The cleaning cylinder is coupled between the upper element and the lower element. The cleaning cylinder has a length substantially similar to the height of the solar panel and includes an internal cylinder, an external cylinder, a plurality of fasteners and at least one microfiber element. The internal cylinder is coupled with the upper element and the lower element, the external cylinder surrounds the internal cylinder, the fasteners are positioned along the external cylinder and the microfiber element is coupled to the external cylinder via the fasteners. The rotation motor is coupled with the rechargeable power source and with the external cylinder and is for rotating the external cylinder and the microfiber element. The processor is coupled with the drive motor and the rotation motor and the transceiver is coupled with the processor. The drive motor is coupled with at least one of the horizontal wheels and the vertical wheels and is for driving at least one of the horizontal wheels and the vertical wheels. The plurality of fasteners are positioned along the external cylinder to give the microfiber element a helix shape along a length of the external cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:

Figures 1A and 1 B are schematic illustrations of the prior art;

Figures 2A-2F are schematic illustrations of a solar panel cleaning cylinder with helix shaped microfiber elements, shown in different views, constructed and operative in accordance with an embodiment of the disclosed technique;

Figures 3A and 3B are schematic illustrations of another solar panel cleaning cylinder with helix shaped microfiber elements, shown in different perspective views, constructed and operative in accordance with another embodiment of the disclosed technique;

Figures 4A and 4B are schematic illustrations of the solar panel cleaning cylinder with helix shaped microfiber elements shown in Figures 2A-3B cleaning a solar panel surface, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figures 5A and 5B are schematic illustrations of a frameless waterless solar panel cleaning robot, constructed and operative in accordance with another embodiment of the disclosed technique;

Figures 6A and 6B are schematic illustrations of the frameless waterless solar panel cleaning robot of Figures 5A and 5B fitted with helix shaped microfiber elements, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figures 7A and 7B are schematic illustrations of the bidirectional cleaning abilities of a waterless solar panel cleaning robot, constructed and operative in accordance with another embodiment of the disclosed technique;

Figure 8 is a schematic illustration of another waterless solar panel cleaning robot fitted with helix shaped microfiber elements, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figures 9A-9C are schematic illustrations of different solar panel row configurations showing challenges for solar panel cleaning robots, constructed and operative in accordance with another embodiment of the disclosed technique;

Figures 10A-10C are schematic illustrations of another frameless waterless solar panel cleaning robot having increased flexibility, constructed and operative in accordance with a further embodiment of the disclosed technique; Figures 11A-11 B are schematic illustrations of the frameless waterless solar panel cleaning robot having increased flexibility of Figures 10A-10C used in cleaning the different solar panel row configurations of Figures 9A-9C, constructed and operative in accordance with another embodiment of the disclosed technique;

Figures 12A-12B are schematic illustrations of a first embodiment of a beam sensor for use with a waterless solar panel cleaning robot shown in a side view and a top view, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figures 12C-12D are schematic illustrations of a second embodiment of a beam sensor for use with a waterless solar panel cleaning robot shown in a side view and a top view, constructed and operative in accordance with another embodiment of the disclosed technique;

Figures 12E-12F are schematic illustrations of the first and second embodiments of the beam sensors of Figures 12A-12D shown in a perspective view, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figures 13A-13B are schematic illustrations of the first and second embodiments of the beam sensors of Figures 12A-12B shown in a side view showing misalignment detection of the wheels of the cleaning robot and the solar panel, constructed and operative in accordance with another embodiment of the disclosed technique;

Figures 14A-14B are schematic illustrations of a solar panel row including a large gap and a bridge, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figure 15 is a schematic illustration of a frameless waterless solar panel cleaning robot capable of crossing the large gap of Figure 14B, constructed and operative in accordance with another embodiment of the disclosed technique;

Figures 16A-16B are schematic illustrations of a solar panel row including a large gap and a bridge showing the cleaning robot of Figure 15 crossing both the large gap and the bridge, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figure 17 shows schematic illustrations of the coupling joint of the frameless waterless solar panel cleaning robot having increased flexibility of Figures 10A-10C, constructed and operative in accordance with another embodiment of the disclosed technique; Figure 18 is a schematic illustration of a further frameless waterless solar panel cleaning robot having increased flexibility, constructed and operative in accordance with a further embodiment of the disclosed technique;

Figure 19 is a schematic illustration of another frameless waterless solar panel cleaning robot capable of crossing the large gap of Figure 14B, constructed and operative in accordance with another embodiment of the disclosed technique;

Figure 20 is a schematic illustration of a locking mechanism for a cleaning robot positioned over a bridge, constructed and operative in accordance with a further embodiment of the disclosed technique; and Figures 21A-21 B are schematic illustrations of other embodiments of the cleaning cylinder of the frameless waterless solar panel cleaning robot showing the coupling of the microfiber fins, constructed and operative in accordance with another embodiment of the disclosed technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art by providing a novel waterless solar panel cleaning robot which includes at least one helix shaped cleaning element made from microfibers. The helix shaped microfibers increase the cleaning efficiency of the cleaning robot of the disclosed technique by creating a directional airflow which moves dust, dirt and debris both forward and downward simultaneously. The helix shaped microfibers of the disclosed technique enable dirt, debris and soiling to be moved efficiently and quickly (for example, over the course of a few meters lengthwise) from the upper section of a solar row to the lower section of the solar row and then swept off to the ground, regardless of the tilt angle of the solar row. The helix shaped cleaning element of the disclosed technique is based upon the shape and physical principles behind an Archimedean screw. The helix shaped microfibers of the disclosed technique thus prevent an excess built-up and accumulation of soiling across the length of a solar row and draw soiling towards the lower end of the solar panels and then off the solar panels. This is particularly useful in the case of fixed angle solar rows wherein the tilt angle of the solar row with respect to the ground may be only a few degrees such that the effect of a gravitational pull on loosened soiling on the solar panel surfaces is negligible and practically non-existent. The helix shaped microfibers thus also reduce excess build-up of dirt and debris on the lower end of the solar panels of a solar row as the cleaning robot moves horizontally along the length of the solar row. The helix shaped microfibers of the disclosed technique also improves the power consumption of the rotation motor used to rotate the central cylinder which rotates the microfiber elements (such as fins). Prior art cleaning robots, which use fins that are positioned in a straight direction, cause increased tension and resistance in the rotation motor, since as the central cylinder rotates, the fins simultaneously impinge upon and brush the solar panel surface with a periodicity. The periodicity can also cause vibrations in the cleaning robot, thus necessitating a framed construction to increase the weight of the cleaning robot. The increased weight of such prior art cleaning robots may dampen the vibrations but this comes at the cost of increased weight which can increase the possibility of damage to the solar panel surfaces. Furthermore, each hit of the fins as they spin around and come in contact with the solar panel surface increases the tension and resistance placed upon the rotation motor, resulting in an increase in power consumption of the rotation motor. According to the disclosed technique, the use of helix shaped microfiber fins reduces the tension and resistance placed upon the rotation motor as it spins the central cylinder. Due to the helix shape of the microfiber fins, the microfiber fins are in constant contact with the solar panel surfaces, thus substantially eliminating any periodicity of the contact of the microfiber fins with the solar panel surface. The substantial elimination of the periodicity results in a substantial reduction in vibrations of the central cylinder as it spins around. According to the disclosed technique, the helix shape of the microfiber fins improves power consumption of the rotation motor by around 20-30% as the helix shape allows for less resistance and tension in the rotation motor.

According to another aspect of the disclosed technique, the cleaning robot of the disclosed technique can achieve an airflow cleaning effect similar to the airflow cleaning effect of the helix shaped cleaning element disclosed above (based upon the shape and physical principles behind an Archimedean screw) however without using a helix shaped cleaning element. As described below, a helix shaped cleaning element may have increased production costs due to the forming of a helix shaped opening around a cleaning cylinder. According to the disclosed technique, a similar airflow effect can be achieved by a regular shaped cleaning element, wherein microfiber fins are positioned lengthwise in a straight line. In this embodiment, the upper and lower portions of the cleaning robot are coupled to a cleaning cylinder via flexible joints that enable at least one degree of freedom between the upper and lower portions thereby enabling the upper and lower portions to move independently of one another. A motor in either the upper or lower portion of the cleaning robot can respectively move either the upper or lower portion of the cleaning robot faster along the length of a solar row, thus giving the cleaning robot a slanted or tilted l-shape and enabling the cleaning cylinder to be positioned at an angle to the direction of travel of the cleaning robot. Rotating the microfiber elements with the cleaning cylinder at an angle (either downwards towards the bottom of a solar panel or upwards towards the top of the solar panel) will effectively achieve the same air flow effect based on the principle of the Archimedean screw as the helix shape of the microfiber fins described above, however with reduced production costs.

According to another aspect of the disclosed technique, the cleaning robot of the disclosed technique can also include a novel cleaning element which can adapt to the direction in which the cleaning robot travels, thus enabling bidirectional cleaning, even with a helix shaped cleaning element which has an inherent directionality. The novel cleaning element allows for the helix shape to change its angle of curvature, thereby enabling the helix shape to be shaped appropriately for left direction cleaning or right direction cleaning. The helix shape of the cleaning element can also be adjusted and modified so that the angle of curvature is appropriate for the tilt angle of the solar panels as well as the direction of the wind passing over the solar row. For example, in the case of fixed angle solar panels which tend to have a relatively small tilt angle, a larger angle of curvature of the helix shape may be needed to increase the directional airflow downward as the effect of gravity on loosened soiling will be less. In the case of variable angle solar panels (i.e. solar trackers), which tend to have relatively larger tilt angles, a smaller angle of curvature of the helix shape may be used as the effect of gravity on loosened soiling will be greater.

In one embodiment of the disclosed technique, the novel cleaning element includes a central cylinder with a plurality of rings interspersed along the length of the central cylinder. The rings can rotate around the central cylinder, each ring having a predetermined amount of rotation. Microfiber fins are coupled with the rings. The rotation of the rings thus enables the microfiber fins to take different helix shapes, whether appropriate for left/right direction cleaning and/or for modifying the angle of curvature of the helix shape. In another embodiment of the disclosed technique, the novel cleaning element includes a plurality of interconnected cylinders and rings which can rotate from a first travel direction to a second travel direction, and vice-versa. In this embodiment as well, the microfiber fins are coupled with the rings. In both embodiments described above, the friction and touch of the helix shaped microfibers on the surface of the solar panels as the central cylinder rotates or as the plurality of interconnected cylinders rotate, enables the helix shape to change from the first travel direction to the second travel direction. The cleaning robot of the disclosed technique can thus adapt the cleaning element autonomously to the direction of travel of the cleaning robot over a solar panel surface, thereby increasing the efficiency of the cleaning robot.

The ability of the cleaning element of the disclosed technique to autonomously adjust the helix shape for appropriate cleaning regardless of the direction of travel of the cleaning element over the solar panel surfaces, herein referred to as bidirectional cleaning, has a number of benefits. According to the disclosed technique, in a solar park where cleaning robots are installed, each solar row can be equipped with a docking station on either side of the solar row, thus enabling the cleaning robot to dock at either side of the solar row. For example, the cleaning robot may dock at opposite sides of the solar row every other day. According to the disclosed technique, the cleaning robot can start cleaning directly regardless of which side it docked at the end of its operation on the previous day. There is thus no need for the cleaning robot to return to a specific docking station to begin its cleaning cycle. The ability of the disclosed technique to provide bidirectional cleaning has a number of efficiency benefits for the cleaning robot. For example, the life expectancy of the parts of the cleaning robot may be doubled over cleaning robots which can only clean in one direction, as the cleaning robot of the disclosed technique never has to return to a specific docking station, thus reducing the amount of travel of the cleaning robot each day in half. Enabling bidirectional cleaning also enables the amount of power the cleaning robot needs to pass over and clean a solar row to be reduced, as only a single pass over the surface is needed for the cleaning robot to get from one docking station to another. This enables the rechargeable power source on the cleaning robot to be reduced in size which also reduces the weight of the cleaning robot. This also enables a self-charging solar panel on the cleaning robot to itself be reduced in size, thus further reducing the weight of the cleaning robot. In general, reducing the weight of the cleaning robot while maintaining its cleaning efficiency reduces the chances that the cleaning robot will damage the solar panel surfaces as it passes over them to clean. In some cases where the self-charging panel is part of the docking station instead of being mounted on the cleaning robot, the reduction in size of the self-charging panel on the docking station will reduce the cost of the docking station and possibly also reduce its size, which provides increased efficiency (for example, lower maintenance costs in case of a self-charging panel malfunction). If for some reason, in the solar park the cleaning robot has a docking station on only one side of each solar row, then according to the disclosed technique, the cleaning robot can clean both on the way from the docking station and on its return to the docking station, thus achieving a more efficient cleaning. In addition, if a second pass of the cleaning robot over the solar panels of a solar row is required to amply remove any soiling on the solar row, then the bidirectional cleaning of the disclosed technique affords this. In another embodiment of the disclosed technique, a docking station may be positioned in the middle of a solar row over a large gap between groups of solar panels.

In yet a further aspect of the disclosed technique, the novel cleaning robot of the disclosed technique can be optionally constructed to have either a framed construction or a frameless construction (which eliminates the need for an outer frame while nonetheless maintaining cleaning efficiency). A framed construction enables increased stability whereas a frameless construction enables a significant reduction in weight. According to one embodiment of the disclosed technique, a frameless cleaning robot is possible with high cleaning efficiency while reducing weight and design complexity for a solar panel cleaning robot. The helix shape of the microfiber fins of the disclosed technique allows for smoother rotation of the microfiber fins over the solar panel surface, thereby reducing vibrations and increasing stability even when the cleaning robot has a frameless construction. The robustness and cost effectiveness of the solar panel cleaning robot of the disclosed technique can thus be increased while also minimizing the weight of the cleaning robot, which reduces the pressure of the cleaning robot’s weight on the solar panels, thus reducing the risk of damage to the solar panels when the cleaning robot travels over the frame and surface of the solar panels.

According to another aspect of the disclosed technique, the novel cleaning robot of the disclosed technique can be constructed having a frameless construction wherein a cleaning cylinder of the cleaning robot is coupled with both an upper element and a lower element via respective coupling joints having increased flexibility. The coupling joints can provide independent movement of the upper element with the cleaning cylinder and the lower element with the cleaning cylinder, thereby giving the frameless solar panel cleaning robot up to six degrees of freedom (herein abbreviated DOF). The increased flexibility of such a frameless construction enables the solar panel cleaning robot to easily and seamlessly travel and traverse over solar panel row configurations in which there may be misalignments, both horizontally and vertically, between adjacent solar panels as well as solar panel row configurations in which bridge rails are used to couple adjacent solar panel row sections. In such solar panel row configurations implementing bridge rails, each solar panel row section may be at a different height and a different angle depending on the terrain each section is installed on and also depending on the alignment of the tilt angle of adjacent sections, where an upper bridge rail may be of a different length and spatial configuration as compared to a lower bridge rail. The increased flexibility of the frameless construction of the disclosed technique enables the solar panel cleaning robot to easily and seamlessly cross such bridge rails and keeps the solar panel cleaning robot firmly coupled with each section of the solar panel row regardless of differences in height, angle and length of each bridge rail.

According to a further aspect of the disclosed technique, the novel cleaning robot of the disclosed technique includes a plurality of beam sensors coupled with each corner of the cleaning robot. Each beam sensor includes a pair of beam units, one which transmits a light beam and one which receives the light beam, such as infrared light. The beam units are positioned opposite one another and are placed having an angle and curvature such that the light beam will not be received by the receiver when the cleaning robot travels along a solar panel surface provided the vertical and horizontal wheels of the cleaning robot are properly aligned with the solar panel surface. The light beam will thus only be received when the cleaning robot passes over a gap between adjacent solar panels or when the cleaning robot passes over a bridge coupling two adjacent solar panel row sections. Transmission and reception of the light beam when the cleaning robot travels over the solar panel surface but is not travelling over a gap can thus be used as an indication that the cleaning robot is misaligned with the solar panel surface. Corrections to the positions of the vertical and horizontal wheels of the cleaning robot can then be effected to correct the position of the cleaning robot and to realign it with the solar panel surface. The beam sensors of the disclosed technique can also be embodied using other forms of transmitted and received energy, such as ultrasound beams. In another embodiment of the disclosed technique, the beam sensors may be located above the solar panel, having an angle of 90° between them, each beam sensor being positioned at an angle of 45° from the solar panel. In such an embodiment, instead of the beam from one sensor being blocked by the solar panel from reaching the other sensor, the beam is reflected by the solar panel to the other sensor. Thus a gap between adjacent solar panels is detected by a transmitted beam not being reflected and detected by a receiver sensor.

According to a further aspect of the disclosed technique, the novel cleaning robot of the disclosed technique includes a plurality of extension arms which can aid the cleaning robot in traversing large gaps between adjacent solar panels wherein the gaps are larger than the diameter of the wheels of the cleaning robot yet smaller than the width of the cleaning robot. In such solar panel arrays, there may be a multitude of such large gaps per solar panel row, thus making it costly to install bridges over each large gap to enable the cleaning robot to cross each large gap. In addition, in such solar panel arrays, these large gaps may not be sufficiently large to financially warrant the installation of bridges over such gaps. Thus according to the disclosed technique, extension arms are provided which enable the cleaning robot to easily traverse over such large gaps without the need for the installation of bridges over such gaps. The extension arms can be moved and positioned at different angles such that they do not interfere with bridge rails or other structures which the upper and lower ends of the cleaning robot may come into contact with as it travels over a solar panel row.

It is noted in general that the disclosed technique is described herein with regards to a waterless solar panel cleaning robot for cleaning industrial sized solar parks which may include hundreds of thousands or even millions of solar panels. However the disclosed technique is not limited to industrial sized solar parks and can equally be used and implemented in commercial and industrial setups, such as solar panels installed on the roofs of buildings, gas stations, parking garages, above an agricultural field, industrial sized buildings and other such similar structures.

Reference is now made to Figures 2A-2F, which are schematic illustrations of a solar panel cleaning cylinder with helix shaped microfiber elements, shown in different views, generally referenced 100, 120, 140, 150, 160 and 170 respectively, constructed and operative in accordance with an embodiment of the disclosed technique. Identical elements between the figures are shown using identical reference numbers. With reference to Figure 2A, shown schematically from a top view is a cleaning cylinder 102 which can rotate around its central axis (not shown) in either direction (i.e., clockwise or counter-clockwise), as shown by a rotation arrow 108. Cleaning cylinder 102 includes a track 104 into which a microfiber fin (not shown) or microfiber element (not shown) can be inserted. As shown by two vertical lines 106A and 106B which are parallel to the length direction of cleaning cylinder 102, track 104 extends along the length of cleaning cylinder 102 from line 106A to line 106B thus giving track 104 a helix shape around cleaning cylinder 102. With reference to Figure 2B, shown in a perspective view is a cleaning cylinder 122 including three tracks 124A, 124B and 124C. Cleaning cylinder 122 is shown as a hollow cylinder. Shown more clearly is an opening 126 in the track (opening 126 forms part of track 124B) into which a microfiber fin (not shown) or microfiber element (not shown) can be inserted into. Opening 126 allows for easy removal and replacement of worn out microfiber fins and/or elements. Tracks 124A-124C each have a helix shape around the length direction of cleaning cylinder 122. As mentioned above, the cleaning cylinder may be the height of a solar row (not shown) such that as it passes over the length of the solar row, and thus the entire height of the solar row may be cleaned in a single pass. Given that a solar row may typically have a height ranging between 2-10 meters, cleaning cylinder 122 also includes a plurality of support beams 128 which run along the inside hollow of cleaning cylinder 122 to prevent sagging of cleaning cylinder 122. Each one of plurality of support beams 128 is parallel to the length direction of cleaning cylinder 122. Plurality of support beams 128 strengthens the integrity of cleaning cylinder 122 such that it does not sag along its length, especially while rotating. Whereas four support beams are shown in Figure 2B, any plurality of support beams (i.e., at least two) are possible. Since cleaning cylinder 122 rotates, each one of plurality of support beams 128 should be evenly spaced along the inside hollow of cleaning cylinder 122 to avoid unstable rotation of cleaning cylinder 122. Other types of support beam arrangements are possible, such as internal support ribs (not shown) placed cross-sectionally along the length of cleaning cylinder 122, support beams having other shapes and configurations and the like. It is noted that tracks 124A-124C can be manufactured as integral components of cleaning cylinder 122. Tracks 124A-124C can also be manufactured as separate components and attached to cleaning cylinder 122 by a glue, screws, rivets, an adhesive as well as other fastening techniques (depending on the material cleaning cylinder 122 is made from), such as soldering and welding. In general, cleaning cylinder 122, opening 126 and plurality of support beams 128 can be made from any of the following materials: plastics, fiber reinforced plastics, fiberglass, carbon fibers, aluminum or stainless steel. The tracks can also be manufactured as separate ring elements which are placed and affixed along the length of the cleaning cylinder, with the microfiber elements being coupled between adjacent ring elements (such an embodiment is shown below in Figures 6A and 6B). In addition, cleaning cylinder 122 is shown having three tracks, however cleaning cylinder 122 can be embodied having two tracks as well as four tracks. The inventors have discovered that using a single track with a single microfiber fin compromises the stability of cleaning cylinder 122 as it rotates, causing vibrations and a lack of balance during rotation. In addition, the inventors have also discovered that using five tracks or more may cause the microfiber fins in each of the tracks to touch one another as they rotate, thereby reducing the created directional airflow as described below in Figures 4A-4B. The use of too many microfiber fins along the length of cleaning cylinder 122 which causes a reduction in the created directional airflow is not just a function of the length of cleaning cylinder 122 but also the angle of curvature of the tracks, as described below. A cross-section along lines A-A in Figure 2B of cleaning cylinder 122 is shown below in Figure 2C.

With reference to Figure 2C, a cross-section of cleaning cylinder 122 along lines A-A is shown. As can more easily be seen, cleaning cylinder 122 has three tracks 124A, 124B and 124C placed along its outer surface in a helix shape. Shown clearly as well is opening 126 into which a microfiber fin (not shown) can be inserted. Also shown clearly is plurality of support beam 128, wherein each support beam is evenly spaced from its neighboring support beam. A curve 142 delineates the beginning and end of track 124B along the length of cleaning cylinder 122. As explained in further detail below in Figure 2F, the length of curve 142 can be used to determine the angle of curvature of a given track. With reference to Figure 2D, cleaning cylinder 122 of Figure 2B is shown again in a perspective view however this time with a plurality of microfiber fins 152A, 152B and 152C inserted into each of the respective openings (not labeled) of tracks 124A, 124B and 124C. As can be seen, each one of plurality of microfiber fins 152A, 152B and 152C has a helix shape due to the helix shape of tracks 124A-124C. The use of an opening in each of tracks 124A-124C enables plurality of microfiber fins 152A, 152B and 152C to be easily coupled and decoupled from cleaning cylinder 122, for example when the microfiber fins need to be replaced and/or repaired.

With reference to Figure 2E, cleaning cylinder 122 of Figure 2C is shown again in a cross-section view however this time with plurality of microfiber fins 152A, 152B and 152C inserted into each of the respective openings (not labeled) of the tracks (not labeled). Even though each one of plurality of microfiber fins 152A-152C appears to have a triangular slice shape, the shape of each one of plurality of microfiber fins 152A-152C is actually helical since the tracks into which the microfiber fins are inserted into are helical along the length direction (i.e., into the page) of cleaning cylinder 122. With reference to Figure 2F, a cross-section of a cleaning cylinder 172 is shown showing a single track 176 into which a single microfiber fin 178 has been inserted into. Single track 176 begins at a point 174 ₁ on the outer surface of cleaning cylinder 172 and ends at a point 174 ₂ on the outer surface of cleaning cylinder 172. By extending the lines via which single microfiber fin 178 extends from cleaning cylinder 172 towards the center of cleaning cylinder 172, an angle A (referenced by 180) can be formed. Angle A between the beginning and end of single track 176 along the length of cleaning cylinder 172 is the angle of curvature of single track 176, herein referenced as angle of curvature 180. With reference back to Figures 2D and 2E, in order to maintain the balance and stability of the plurality of microfiber fins as they rotate around as cleaning cylinder 122 rotates, the angle of curvature of each track must be substantially the same and each of plurality of microfiber fins 152A-152C must be evenly spaced apart from one another. Referring back to Figure 2F, as an example, angle of curvature 180 can range anywhere from 45° per meter along the length of cleaning cylinder 172 to 150° per meter. However other angles of curvature per meter are possible depending on the number of microfiber fins used in cleaning cylinder 172. The angle of curvature may need to be optimized for a given solar array in a given solar park however the angle of curvature per meter must be greater than 0° per meter in order to ensure that each track has a helix shape along the length of cleaning cylinder 172.

As shown, for example in Figures 2B and 2D, the helix shape of tracks 124A, 124B and 124C effectively give plurality of microfiber fins 152A-152C a shape resembling an Archimedean screw. Whereas the concept of an Archimedean screw is usually associated with hydraulics, the concept applies equally as well to the motion and flow of gases, such as the airflow generated by the rotation of plurality of microfiber fins 152A-152C as cleaning cylinder 122 rotates. As shown in further detail below in Figures 4A and 4B, the rotation of cleaning cylinder 122 with the rotation of the microfiber fins will cause an airflow to move either upwards or downwards along the length of cleaning cylinder 122 (depending on its direction of rotation). Thus similar to an Archimedean screw, which can be used to displace water upwards against the natural downwards force of gravity, rotating cleaning cylinder 122 (in one direction) will cause an upwards directional airflow. Rotating cleaning cylinder 122 in the opposite direction will cause a downwards directional airflow, which can be used, as described below, for efficiently removing dirt, dust and debris from a solar panel surface without using water or any other liquids.

Reference is now made to Figures 3A and 3B, which are schematic illustrations of another solar panel cleaning cylinder with helix shaped microfiber elements, shown in different perspective views, generally referenced 200 and 210 respectively, constructed and operative in accordance with another embodiment of the disclosed technique. Identical elements between the figures are shown using identical reference numbers. Shown in these figures is another embodiment of the cleaning cylinder which includes two microfiber fins/elements as opposed to the three microfiber fins/elements shown above in Figures 2A-2F. With reference to Figure 3A, a cleaning cylinder 202 is shown with two microfiber fins 204A and 204B in a first perspective view. Cleaning cylinder 202 includes tracks (not shown) as well as support beams (not shown). The angle of curvature of the tracks may be 150° per meter, for example. With reference to Figure 3B, cleaning cylinder 202 and microfiber fins 204A and 204B are shown in a second perspective view. Clearly shown is the helix shape of microfiber fins 204A and 204B around cleaning cylinder 202.

Reference is now made to Figures 4A and 4B, which are schematic illustrations of the solar panel cleaning cylinder with helix shaped microfiber elements shown in Figures 2A-3B cleaning a solar panel surface, generally referenced 250 and 280 respectively, constructed and operative in accordance with a further embodiment of the disclosed technique. Identical elements between the figures are shown using identical reference numbers. It is noted that both of Figures 4A and 4B show only the solar panel cleaning cylinder of the disclosed technique cleaning a solar panel surface to illustrate the disclosed technique. As described below in Figures 5A-8, the cleaning cylinder of the disclosed technique forms part of a solar panel cleaning system which includes other components, such as a processor, at least one motor, an outer structural frame (for covering the internal components of the cleaning system), a plurality of wheels, a rechargeable power source, at least one solar panel for self-charging the rechargeable power source, at least one sensor (for example, a position sensor, an infrared sensor, an ultrasound sensor and the like), a power source (e.g., battery) charge controller, a locking/parking mechanism (which may be optional) as well as a wireless transceiver (all not shown), which are described below. With reference to Figure 4A, shown is a solar row 252 including a plurality of solar panels 254 placed side by side. In general, solar row 252 is mounted at an angle, giving solar row 252 an incline with respect to the ground and thus having an upper end 256 and a lower end 258. Figure 4A shows three different views of the solar panel cleaning cylinder. A first view 251 A shows a solar panel cleaning cylinder 260 from a top view cleaning plurality of solar panels 254. A second view 251 B shows solar panel cleaning cylinder 260 from a side view cleaning plurality of solar panels 254. A third view 251 C shows solar panel cleaning cylinder 260 from a side view showing the rotation and movement of solar panel cleaning cylinder 260.

In first view 251 A, cleaning cylinder 260 includes three tracks 262 from which three microfiber fins (not shown in first view 251 A) extend. Cleaning cylinder 260 rotates about its central axis and is positioned such that as cleaning cylinder 260 rotates, the microfiber fins touch the surface of plurality of solar panels 254. A motorized mechanism (not shown) moves cleaning cylinder 260 along the length direction of solar row 252, as shown by an arrow 264. Due to the helix shape of tracks 262, a directional air flow which is both forward moving and downward moving is created as cleaning cylinder 260 rotates. As explained above, this is due to the helix shape of tracks 262 which gives cleaning cylinder 260 a shape similar to an Archimedean screw. The direction of the directional air flow is schematically shown in Figure 4A as a plurality of arrows 266. As shown more clearly in second view 251 B, which shows that solar row 252 has upper end 256 and lower end 258 thereby giving plurality of solar panels 254 an incline towards the ground, as cleaning cylinder 260 rotates and cleans dirt, dust and debris from the surface of plurality of solar panels 254, dirt, dust and debris is generally moved downward off the surface of the solar panels, as shown by an arrow 268.

According to the disclosed technique, the diagonally inclined directional air flow generated by the helix shaped microfiber fins which rotate around cleaning cylinder 260 improves the waterless cleaning of plurality of solar panels 254. The diagonally inclined directional air flow moves soiling located on upper end 256 downward towards lower end 258 and eventually off the surface of the solar panels due to the helix shape of the microfiber fins along with the force of gravity due to the inclined shape of solar row 252. It is noted that the helix shaped microfiber fins enable soiling located at upper end 256 of the solar panels to be moved downward and off of the solar panel surfaces by lower end 258 over a horizontal distance of a few meters as cleaning cylinder 260 travels in the direction of arrow 264. The general downward direction in which soiling is moved, as shown by arrow 268, improves the cleaning of plurality of solar panels 254 even in fixed angle solar rows where the tilt angle of the solar row may only be a few degrees and the effect of gravity on loosened soiling is minimal.

In third view 251 C, cleaning cylinder 260 is shown from the side wherein its direction of rotation is shown by an arrow 270. Shown as well are three microfiber fins 272A-272C which extend from tracks 262. The helix shape of the microfiber fins is also clearly shown. Due to the clockwise rotation of cleaning cylinder 260, as shown by arrow 270, the helix shape of microfiber fins 272A-272C causes air to flow downwards, as shown in second view 251 B by arrow 268. It is noted that directional air flow 266 is achieved because tracks 262 extend along the length of cleaning cylinder 260 and because microfiber fins are used, which together generate a substantial movement of air. In one embodiment, microfiber fins 272A-272C may each be a single material which is threaded through a respective track. In another embodiment, microfiber fins 272A-272C may each be a plurality of smaller length microfiber fins which are stitched together. In this embodiment, optionally the smaller length microfiber fins located at lower end 258 can be thicker and/or slightly longer and/or wider than the microfiber fins located at upper end 256 in order to impinge upon the surface of the solar panels at the lower end with more force in order to improve cleaning at lower end 258 where there is potentially more soiling. Microfiber fins 272A-272C provide for enhanced airflow and also less potential damage to solar panel surfaces in comparison to brushes and bristles as described in the prior art. Besides loosening soiling from the solar panel surfaces, the helix shaped microfibers of the disclosed technique also generates a directional airflow which guides and directs soiling forward and downward off the solar panel surface.

It is noted that cleaning cylinder 260 can be made having different diameters as well as being made from different materials. Similar to what was mentioned above about the microfiber fins being thicker and/or slightly longer at lower end 258, cleaning cylinder 260 might have a variable diameter along its length, increasing slightly in diameter from upper end 256 to lower end 258, such that the microfiber fins nearer to lower end 258 impinge upon the solar panel surface with greater force. The actual diameter of cleaning cylinder 260 and any variation in diameter of cleaning cylinder 260 along its length is a design choice that can be optimized by the worker skilled in the art taking into account the desire to remove high levels of soiling located on the lower end of a solar row while nonetheless maintaining the flexibility of helix shaped microfiber fins to generate an enhanced directional airflow for dusting away soiling on the solar panel surfaces. For example, the cleaning cylinder may be made from aluminum, having a diameter of 70 millimeters (herein abbreviated as mm). According to the disclosed technique, there is also a tradeoff between the diameter size of the cleaning cylinder and how close the microfiber fins are positioned relative to the solar panel surface. Cleaning cylinder diameter size as well as closeness of the microfiber fins to the solar panel surface are thus also design choices which can be optimized by the worker skilled in the art. For example, the diameter of the cleaning cylinder may be reduced from 70 mm to 50 mm along its length in order to increase the clearance of the cleaning cylinder from obstacles that might be present on the solar panel array to be cleaned. A gradual reduction in diameter of the cleaning cylinder means that in turn the distance between the microfiber fins and the solar panel surface will increase. Thus the microfiber fins in such an embodiment will require an extension, in this example of at least 10 mm, in order to ensure that the microfiber fins sufficiently make contact with the solar panel surface as the cleaning cylinder rotates. It is noted that a change in the length of the microfiber fins can also change the dynamic behavior of the microfiber fins and can also influence the quality of the cleaning. The change in the dynamic behavior of the microfiber fins may also change the physical strength of the cleaning cylinder, potentially requiring a commensurate change in the internal structure of the cleaning cylinder in order to strengthen it and provide ample support for the rotating microfiber fins. These considerations are design and optimization choices which are known to the worker skilled in the art.

Whereas the helix shaped microfiber fins rotating around cleaning cylinder 260, as shown in Figure 4A, generates an improved directional air flow for removing soiling from solar panel surfaces without water, the configuration of cleaning cylinder 260 and microfiber fins 272A-272C nonetheless has the limitation of unidirectional cleaning. With reference to Figure 4B, in a scenario wherein cleaning cylinder 260 finished cleaning solar row 252 and is located on the opposite side of the solar row and cleaning cylinder 260 is then used, for example on a subsequent day, to again pass over solar row 262 to clean it in the opposite direction, cleaning cylinder 260 is to be rotated in the opposite direction. As shown in Figure 4B are three similar views to Figure 4A, namely a first view 281 A from the top of solar row 252, a second view 281 B from the side along the length of solar 252 and a third view 281 C from the side along the length of cleaning cylinder 260. As shown in first view 281 A, cleaning cylinder 260 is to move in the direction of an arrow 282, in the opposite direction of arrow 264 (Figure 4A), in order to clean solar row 252 from the opposite side without having to return cleaning cylinder 260 to the position it was initially in in Figure 4A. In third view 281 C, the opposite rotation direction of cleaning cylinder 260 is shown by an arrow 288, which is a counter-clockwise direction. As explained above, due to the shape of microfiber fins 272A-272C, when cleaning cylinder 260 rotates in the direction of arrow 288, an airflow in the direction of an arrow 284 is generated, similar to the directional flow of a liquid when used with an Archimedean screw. Cleaning cylinder 260 must rotate in the direction of arrow 288 to move dirt, dust and debris off the surface of the solar panels in the direction of arrow 282, otherwise any remaining dirt, dust and debris will simply be spread over the surface of solar row 252 as cleaning cylinder 260 moves in the direction of arrow 282.

Due to the helix shape of microfiber fins 272A-272C and tracks 262, rotating cleaning cylinder 260 in the direction of arrow 288 will cause a directional air flow in the direction of an arrow 286 (i.e., opposite the direction of arrow 266 (Figure 4A)), which is both forward and upward along the length of solar row 252. As shown in second view 281 B, the opposite rotation direction of cleaning cylinder 260 will cause an upward diagonally inclined directional air flow, shown as arrow 284. Even though cleaning cylinder 260 moving in the direction of arrow 282 will move soiling forward along the length of solar row 252, due to the incline of the solar row and the general upward movement of soiling in the direction of arrow 286, dirt, dust and debris will not be amply removed from the surface of the solar panels. As mentioned above, solar panel cleaning cylinder 260 can effectively remove soiling from solar panel surfaces by moving dirt, dust and debris both forward and downward simultaneously however solar panel cleaning cylinder 260 as shown in Figures 4A and 4B can only do so effectively in one direction.

In one embodiment of the disclosed technique, as described below in Figures 7A and 7B, the helix shape of the microfiber fins can be shifted depending on the direction of travel of the cleaning robot, thus always moving dirt and debris forward and downward as the cleaning robot moves over the solar panel row, regardless of the direction of travel of the cleaning robot. However according to another embodiment of the disclosed technique, the helix shape of the microfiber fins may be fixed and stationary (i.e., without the ability to change directions), thus providing a directional air flow in both the forward and downward directions in only one direction of travel over the solar panel surface. The use of such an embodiment would be when the following constraints are taken into account. Such a design is more cost effective than the design of the cleaning cylinder of the disclosed technique which enables the helix shape to be adjusted depending on the direction of travel of the cleaning robot, for example when cleaning solar trackers which are parked at a relatively high tilt angle (for example 50°), wherein the gravitational force is strong enough to pull any removed dirt and dust by the microfiber fins downwards, even without the microfiber fins having a helix shape. In addition, rotating a fixed and stationary helix shaped microfiber fin in the reverse direction can be an effective way of removing any stubborn dirt, dust and debris which may have accumulated on the solar panels and were not removed when the cleaning robot cleaned the solar panel surface in the opposite direction.

Reference is now made to Figures 5A and 5B, which are schematic illustrations of a frameless waterless solar panel cleaning robot, generally referenced 300 and 340 respectively, constructed and operative in accordance with another embodiment of the disclosed technique. Identical elements between the figures are shown using identical reference numbers. It is noted that even though cleaning robots 300 and 340 are shown without a frame, this is only optional, and cleaning robots 300 and 340 can be embodied with frames for increased stability as described below in Figure 8. With reference to Figure 5A, shown is frameless waterless solar panel cleaning robot 300 which is capable of bidirectional cleaning, as explained in further detail below in Figures 7A and 7B. Frameless waterless solar panel cleaning robot 300 is shown without any microfiber fins to better describe its construction. Below in Figures 6A and 6B, the frameless waterless solar panel cleaning robot of the disclosed technique is shown with inserted microfiber fins. Cleaning robot 300 includes a cleaning cylinder 302, an upper element 304A and a lower element 304B. Cleaning cylinder 302 is coupled between upper element 304A and lower element 304B, which support cleaning cylinder 302 and enable its rotation around its central axis (not shown). Shown in greater detail below in Figure 5B, cleaning cylinder 302 may be made of two concentric cylinders, an internal cylinder (not shown) and an external cylinder, with the internal cylinder having a smaller diameter than the external cylinder. The external cylinder as shown in Figure 5A is substantially cleaning cylinder 302 upon which a plurality of rings 308 is positioned. The internal cylinder may be stationary (i.e., it does not rotate) and can be directly coupled, via a respective at least one bearing, with upper and lower elements 304A and 304B, thus affording the internal cylinder a degree of flexibility in relation to upper and lower elements 304A and 304B. The external cylinder, such as cleaning cylinder 302, is positioned around the internal cylinder and is coupled with a motor (not shown) for rotating cleaning cylinder 302. The motor can be positioned in upper element 304A or in lower element 304B and can be coupled with cleaning cylinder 302 via a transmission belt (not shown) or directly to form a direct transmission. Thus the internal cylinder enables the upper and lower elements to be coupled while giving them a degree of flexibility while simultaneously allowing the external cylinder to rotate microfiber fins. Upper element 304A includes an upper guide unit 318A, two horizontal wheels 310 and two vertical wheels 312. Lower element 304B includes a lower guide unit 318B, two horizontal wheels 314 and two vertical wheels 316. According to the disclosed technique, at least one horizontal wheel can be used for each of the upper and lower guide units. Also according to the disclosed technique, at least two vertical wheels should be used for each of the upper and lower guide units in order to enable the cleaning robot to deal with gaps and misalignments that might occur between adjacent sections of solar panels in a solar row (not shown). Upper guide unit 318A and lower guide unit 318B along with horizontal wheels 310 and 314 and vertical wheels 312 and 316 are positioned and configured respectively on the upper and lower ends of a solar panel and enable cleaning cylinder 302, upper element 304A and lower element 304B to move over the surface of a solar row. Upper and lower guide units 318A and 318B can be embodied as ultrasonic distance sensors which face the upper and lower sides of the frame of a solar panel (not shown). Such distance sensors measure the distance from their position to the upper and lower sides of the frame of the solar panel. As the expected distance is known based on the distance of each of upper and lower elements 304A and 304B to the frame of the solar panel, the distance sensors can be used to guide cleaning robot 300 as it travels over a solar panel row. For example, if the determined distance of the ultrasonic distance sensors exceeds a predetermined limit, the drive motors (not shown) of upper and/or lower elements 304A and 304B can be used to adjust the position of horizontal wheels 310 and 314 and vertical wheels 312 and 316 to realign cleaning robot 300 such that it remains properly positioned over the frame of the solar panel. In another embodiment, upper and lower guide units 318A and 318B can be embodied as the beams sensors described below in Figures 12A-13B. Solar panels are usually constructed having a frame. As such, horizontal wheels 310 and 314 and vertical wheels 312 and 316 are usually positioned to roll over the frame of the solar panels but not over the actual surface of the solar panels where solar cells are situated. Whereas the aforementioned is desired, this is not required, and vertical wheels 312 and 316 may also be positioned to roll over the actual outer surface of the solar panels.

At least one of upper element 304A and lower element 304B may include at least one drive motor (not shown) for driving at least one of the horizontal and/or vertical wheels. At least one of upper element 304A and lower element 304B may also house a rotation motor (not shown) for rotating cleaning cylinder 302. At least one of upper element 304A and lower element 304B may further include a processor, at least one rechargeable power source and a transceiver (all not shown). The processor is for executing commands as well as storing and collecting data about cleaning robot 300. At least one rechargeable power source is used for providing power to drive the drive motor as well as the rotation motor and also for providing energy to the processor and transceiver. The transceiver, which may be wireless, is for transmitting and receiving signals to and from the processor, for example, from a central management unit, server or computer.

In one embodiment, cleaning cylinder 302 is made from a single cylinder upon which plurality of rings 308 is positioned. Plurality of rings 308 can rotate around the single cylinder and may be positioned within indentations and/or tracks (not shown) in cleaning cylinder 302 which limit the amount of rotation of each one of plurality of rings 308. Cleaning cylinder 302 is rotated via a motor (not shown), thus rotating plurality of rings 308 and the microfiber fins (not shown) coupled with plurality of rings 308. Plurality of rings 308 may be limited in their angular movement to maintain the helix shape of the microfiber fins while cleaning cylinder 302 rotates. Plurality of rings 308 may have sufficient angular movement (for example, up to 90°) to enable the helix shape of the microfibers to change positions depending on the direction of travel of cleaning robot 300, as described below in more detail in Figures 7A and 7B. In another embodiment, a plurality of spacers (not shown) is positioned between adjacent ones of plurality of rings 308. The spacers are hollow cylinders positioned around cleaning cylinder 302 respectively between each one of plurality of rings 308 to ensure that a first one of plurality of rings 308 remains a predetermined distance from an adjacent second one of plurality of rings 308. In this embodiment, plurality of rings 308 may not be limited in terms of their amount of rotation as the spacers ensure that each one of the plurality of rings remain sufficiently apart from one another which ensures that the microfiber fins maintain a helix shape as they rotate around the cleaning cylinder. Each spacer may include at least one ring or button for enabling a microfiber fin to couple directly with the spacer. In another embodiment of the disclosed technique, the plurality of spacers can be of different lengths over the length of the cleaning cylinder and thus the amount of a microfiber fin positioned in a straight line can change along the length of the cleaning cylinder. In this embodiment, the curvature of the helix shape of the microfiber fins can change along the length of the cleaning cylinder. The single cylinder may be hollow and may include support beams (not shown) for increasing the structural integrity of the single cylinder and preventing it from sagging in the middle. The single cylinder can be made from materials such as aluminum, carbon fiber, fiberglass or stainless steel. In another embodiment, cleaning cylinder 302 may optionally include a plurality of cylinders, labeled 306i, 306 ₂ , 306 ₃ and 306 _N , which are coupled via plurality of rings 308, with one ring respectively coupled with a given cylinder. Plurality of cylinders 306i, 306 ₂ , 306 ₃ and 306 _N can be hollow. In both embodiments just described above, either as a single cylinder or a plurality of cylinders, an internal cylinder is positioned within cleaning cylinder 302 in order to couple the upper and lower elements of the cleaning robot. As mentioned above, the internal cylinder does not rotate is remains stationary while the single cylinder or the plurality of cylinders rotate in order to rotate the microfiber fins. As described in further detail below in Figures 7A and 7B, in one embodiment, plurality of rings 308 are positioned over the cleaning cylinder 302 and in another embodiment, plurality of rings 308 mechanically couple adjacent ones of plurality of cylinders 306I-306 _N together while nonetheless allowing for a degree of relative rotation between adjacent cylinders. In this embodiment, plurality of cylinders 306i, 306 ₂ , 306 ₃ and 306 _N all rotate around the central axis of cleaning cylinder 302. In both embodiments, an internal cylinder (not shown) is positioned within plurality of cylinders 306i, 306 ₂ , 306 ₃ and 306 _N or within cleaning cylinder 302, thus coupling the upper and lower elements together while enabling the cleaning cylinder or the plurality of cylinders to rotate freely. As cleaning cylinder 302 may typically range from 2-10 meters in length, each one of plurality of 306i, 306 ₂ , 306 ₃ and 306 _N may include support beams (not shown) per cylinder and/or may be filled with a material (such as foam, cardboard, internal ribs and the like), for increased strength and robustness, in order to prevent cleaning cylinder 302 from sagging in the middle. Regardless of the embodiment regarding the construction of cleaning cylinder 302, in case cleaning cylinder 302 is longer than 2 meters, at least one central wheel (not shown) may optionally be added to the middle (or middle sections) of cleaning cylinder 302. In one embodiment, the cleaning cylinder is thus split into at least two separate cleaning cylinders (not shown) coupled together midway, in order to prevent sagging in the middle of the cleaning cylinder. In such an embodiment, an internal cylinder (not shown) would still couple the upper and lower elements together and the at least one central wheel could be coupled directly with the internal cylinder for added support. Each cleaning cylinder in this embodiment would be coupled with a separate motor for respectively rotating the cleaning cylinder. In another embodiment, the cleaning cylinder may remain a single cleaning cylinder with a plurality of wheels threaded through the cleaning cylinder and each coupled to the cleaning cylinder with a bearing.

As shown, cleaning robot 300 does not include a frame, its construction and structure including the cleaning cylinder and two guide units for guiding the cleaning robot over a solar panel surface. Thus in one embodiment of the disclosed technique, cleaning robot 300 is a frameless cleaning robot, thereby reducing the overall weight and complexity of the cleaning robot, and providing better flexibility to the cleaning robot. In another embodiment of the disclosed technique (not shown), cleaning robot 300 may include at least two profiles extending from upper element 304A to lower element 304B, thereby providing cleaning robot 300 with a frame (not shown), providing better stability to the cleaning robot. A longitudinal cross-section of cleaning cylinder 302 along a plurality of arrows B-B, labeled 320, is shown below in Figure 5B.

With reference to Figure 5B, the inside of cleaning cylinder 302 is shown. In one embodiment (as shown), cleaning cylinder 302 includes a hollow 342 which includes two interlocking concentric cylinders 344 ₁ and 344 ₂ , which are coupled with upper guide unit 318A. In this embodiment, cleaning cylinder 302 is embodied as a single cylinder. Interlocking concentric cylinder 344 ₂ , may be coupled with a rotation motor (not shown), for rotating cleaning cylinder 302, whereas interlocking concentric cylinder 344 ₁ remain stationary and couples with the upper and lower elements (respectively not labeled and not shown). In another embodiment (not shown), cleaning cylinder 302 may include plurality of cylinders 306i, 306 ₂ , 306 ₃ and 306 _N (Figure 5A) (not shown in Figure 5B) positioned around the outside surface of hollow 342 between plurality of rings 308, thereby enabling cleaning cylinder 302 to fully rotate while nonetheless enabling relative rotation between plurality of cylinders 306i, 306 ₂ , 306 ₃ and 306 _N as described further below. In the embodiment shown, a plurality of support beams or internal ribs (both not shown) can be placed inside hollow 342 for added support and robustness of cleaning cylinder 302.

Reference is now made to Figures 6A and 6B, which are schematic illustrations of the frameless waterless solar panel cleaning robot of Figures 5A and 5B fitted with helix shaped microfiber elements, generally referenced 370 and 390 respectively, constructed and operative in accordance with a further embodiment of the disclosed technique. Identical elements between the figures are shown using identical reference numbers. With reference to Figure 6A, a cleaning cylinder 372 is shown including a external cylinder 373 over which a plurality of rings 378 is placed. As mentioned above, cleaning cylinder 372 can also be embodied as a plurality of cylinders (not shown) which are coupled together respectively via plurality of rings 378. Shown in Figure 6A is a plurality of microfiber fins 374 which are coupled to cleaning cylinder 372 at a plurality of connection points 380. Connection points 380 are respectively located on plurality of rings 378. Connection points 380 may be embodied as clip fasteners such that the microfiber fins can be snapped into connection points 380. In this embodiment for example, the edge of each one of plurality of microfiber fins 374 which is to be coupled with connection points 380 is sewn as a hem with a plastic wire or a metal wire having a plastic cover (not shown) running through the hem. The hem is not limited to simply folding over an edge or end section of the microfiber fin. The wire can be placed in the middle of the microfiber fin, which can then be folded over in two with the wire placed in the center, thus also forming a hem which can be inserted into the connection points. The hem with the wire on each one of plurality of microfiber fins 374 is what is inserted into connection points 374 for coupling plurality of microfiber fins 374 to external cylinder 373. It is noted that the distance between connection points 380 can be uniform or non-uniform. In the case of them being uniform, plurality of microfiber fins 374 can have a uniform curvature regarding its helix shape. In the case of them being non-uniform, plurality of microfiber fins 374 can have a helix shape which changes its curvature along the length of external cylinder 373.

Connection points 380 may also be embodied as dials or buttons which can be rotated between two positions, an open position and a closed position (for example, being 90° or 180° apart), wherein connection points 380 are positioned directly on rings 378. In this embodiment, the microfiber fins can be coupled to connection points 380 directly and locked in place in the closed position. Rotating connection points 380 to the open position will enable a microfiber fin to be quickly removed and replaced. For example, in the case of an old microfiber fin, the old microfiber fin can be easily removed and replaced with a fresh microfiber fin which can then be locked into position by rotating the connection points to the closed position. The closed position thus still leaves some flexibility for the button or dial to rotate along its axis, thus enabling a smooth change of the microfiber fin helix direction when changing the direction of cleaning (or when rotating the cleaning cylinder).

Cleaning robot 370 includes three microfiber fins, thus each one of plurality of rings 380 includes three respective connection points. Connection points 380 may be similar to opening 126 (Figure 2B) for coupling microfiber fins 374 with cleaning cylinder 372. As shown, cleaning robot 370 includes an upper element 376A and a lower element 376B, similar to upper element 304A and lower element 304B (Figures 5A and 5B). Cleaning robot 370 also includes an interlocking cylinder 386 which couples cleaning cylinder 372 with upper element 304A and a rotation motor (not shown) for rotating cleaning cylinder 372 and microfiber fins 374. As shown, cleaning cylinder 372 can rotate clockwise around its central axis (not shown), as shown by an arrow 382, or counter-clockwise around its central axis, as shown by an arrow 384. As mentioned above, cleaning cylinder 370 may include an internal cylinder (not shown) which is directly coupled with upper element 376A and lower element 376B via at least one bearing, thus enabling cleaning cylinder 370 a degree of flexibility in relation to upper element 376A and lower element 376B. External cylinder 373 is positioned concentrically around the internal cylinder and is coupled with the rotation motor, thus enabling external cylinder 373 to rotate and thereby rotate plurality of microfiber fins 374 accordingly.

With reference to Figure 6B, a close-up and transparent view is shown of cleaning cylinder 372 and its coupling with upper element 376A. Connection points 380 are more clearly shown, for example as clip fasteners to which the hemmed edge of a microfiber fin can be snapped into, showing the coupling of microfiber fins 374 to rings 378 via connection points 380. Also shown more clearly is the extension and coupling of interlocking cylinder 386 with cleaning cylinder 372. Schematically shown is a portion of an internal cylinder 392 over which external cylinder 373 is positioned. Internal cylinder 392 may be rigidly coupled with upper element 376A whereas external cylinder 373 is coupled with a rotation motor (not shown) that is coupled with interlocking cylinder 386 for rotating external cylinder 373 and the microfiber fins.

Reference is now made to Figures 7A and 7B, which are schematic illustrations of the bidirectional cleaning abilities of a waterless solar panel cleaning robot, generally referenced 420 and 460 respectively, constructed and operative in accordance with another embodiment of the disclosed technique. With reference to Figure 7A, shown is a cleaning cylinder 421 in various states, with a left travel state 432, a center state 434 and a right travel state 436. Cleaning cylinder 421 is schematically shown having a single central cylinder 422 over which are coupled a plurality of rings 424. Figure 7A only shows four rings, however the figure is brought only as an example to explain the disclosed technique, and other numbers of rings are possible. Upon each one of plurality of rings 424 is a respective connection point 426. As mentioned above, the number of connection points on a given ring is related, usually in a 1 :1 manner, with the number of microfiber fins to be coupled with the cleaning cylinder. Thus in general, each one of plurality of rings 424 will have between 2-4 connection points respectively when 2-4 microfiber fins are used per cleaning cylinder. A microfiber fin in different positions along the length of cleaning cylinder 421 is shown, labeled as microfiber fin positions 430I-430 ₇ . The microfiber fin is coupled with cleaning cylinder 421 via respective connection points 426. A central axis 428 running along the length of cleaning cylinder 421 is shown, delineated as a dotted line. In microfiber fin position 430i, connection points 426 are not in line with central axis 428 and the microfiber fin forms an angle 440i with central axis 428. As the bottom most portion of central cylinder 422, labeled as portion 423, is rotated counter-clockwise, shown by a plurality of arrows 438, plurality of rings 424 begin to rotate clockwise, thereby rotating the microfiber fin clockwise and changes its angle of curvature. The rotation of portion 423 causes the microfiber fin to move to microfiber fin position 4302 thereby forming an angle 440 ₂ with central axis 428. As can be seen, angle 440 ₂ is smaller than angle 440i. Likewise, the continued rotation of portion 423 causes the microfiber fin to move to microfiber fin position 430 ₃ thereby forming an angle 440 ₃ with central axis 428 which itself is smaller than angle 440 ₂ . In center state 434, microfiber fin position 4304 is in line and parallel to central axis 428. As portion 423 continues to be rotated counter-clockwise, the angle between central axis 428 and the position of the microfiber fin begins to grow on the other side of the central axis. As shown, microfiber fin position 430 ₅ forms a small angle 4404 with central axis 428. This angle grows in microfiber fin position 430e, forming a larger angle 440 ₅ and ending with microfiber fin position 430 ₇ , forming an angle 440 ₆ . Adjacent ones of plurality of rings 424 are mechanically designed to rotate a predefined amount relative to one another, thus enabling cleaning cylinder 421 to shift from a left travel state 432 to a right travel state 436 and vice-versa. For example, this can be achieved by a protrusion (not shown) on each one of plurality of rings 424 and grooves of different lengths (not shown) within the portions of central cylinder 422 over which plurality of rings 424 are positioned. The grooves thus enable the protrusions to move plurality of rings 424 along the length of each respective groove. By progressively increasing the length of the grooves from a top portion of central cylinder 422 to a bottom portion (as shown in Figure 7A), plurality of rings 424 can rotate progressively more, thus enabling the helix shape of the microfiber fins to change accordingly depending on the direction of travel of the cleaning robot. Connection point 426 on the uppermost ring may not have a groove at all and thus may be stationary whereas each connection point 426 below the uppermost ring would have a groove which is progressively longer thus enabling a longer rotation of the connection points on each successive ring towards the bottommost ring. As another example, as shown, an upper ring 442 remains fixed such that its respective connection point 426 always remains in line with central axis 428. A lower ring 444 has the most amount of freedom to rotate around central axis 428, with its respective connection point 426 moving from a left position forming angle 440i to a right position forming angle 440e- Since the microfiber fin is coupled with cleaning cylinder 421 via connection points 426, the rotation of the connection points’ results in a rotation of the relative position and shape of the microfiber fin. The amount of movement of each ring can thus be determined by spacers (not shown) placed between each one of the rings as well as the length of the microfiber fin between each connection point 426. The rings between upper ring 442 and lower ring 444 have increased degrees of rotation moving from upper ring 442 to lower ring 444. The amount of rotation of a given ring may be predetermined and fixed such that once a ring reaches it maximum amount of relative rotation between adjacent rings, further rotation in the same direction will rotate the entire ring while the central cylinder rotates with it. Thus in left travel state 432, when cleaning cylinder 421 may be travelling leftward over a solar panel surface, rotating cleaning cylinder 421 in a clockwise direction, as shown by an arrow 439, will not rotate plurality of rings 424 any further, thereby enabling the microfiber fin to maintain its helix shape while cleaning cylinder 421 rotates in one direction. Likewise in right travel state 436, when cleaning cylinder 421 may be travelling rightward over a solar panel surface, rotating cleaning cylinder 421 in a counter-clockwise direction, as shown by arrow 438, will not rotate plurality of rings 424 any further, thereby enabling the microfiber fin to maintain its helix shape while cleaning cylinder 421 rotates in the other direction.

According to the disclosed technique as shown in Figure 7A, bidirectional cleaning with a microfiber fin having an adjustable helix shape is possible, wherein the helix shape can be rotated from a clockwise position to a counter-clockwise position, thus enabling a forward and downward directional air flow being generated by the cleaning cylinder regardless of the direction of travel of the cleaning cylinder. In one embodiment of the disclosed technique, a motor, such as an actuator (not shown), may be used to rotate lower ring 444 from left travel state 432 to right travel state 436 and vice-versa. In this embodiment, the actuator can also be used to adjust and lock the angle of curvature of the helix shape of the microfiber elements, thereby enabling different angles of curvature for the helix shape of the microfiber elements travelling in a given direction. In another embodiment of the disclosed technique, since cleaning cylinder 421 is positioned such that the microfiber fin touches and brushes up against the surface of a solar panel, the friction caused by the microfiber fin touching the solar panel surface may be sufficient to autonomously rotate lower ring 444 from one travel state to another. It is noted that friction may not be necessary to rotate lower ring 444 from one travel state to another. The centrifugal force of air present in the rotation cleaning cylinder 421 (without even being in contact with the surface of the solar panels) is sufficient to change the helix shape of the microfiber elements. As an example of this embodiment, in left travel state 432, when a rotation motor (not shown), rotates cleaning cylinder 421 in a counter-clockwise direction, the touch and friction of the microfiber fin, especially in the vicinity of lower ring 444, will cause lower ring 444 to start rotating in a clockwise direction until it reaches its position in right travel state 436. This embodiment avoids the need for a specific motor to shift the microfiber fin from one helix shape to another. Thus the mere rotation of cleaning cylinder 421 can be used to autonomously switch the helix shape of the microfiber fin from a left travel position to a right travel position, thereby enabling bidirectional cleaning even with microfiber fins in a helix shape.

With reference to Figure 7B, the movement of a microfiber fin from a first helix shape to another helix shape, thereby enabling bidirectional cleaning, is shown via a cross-sectional view of a cleaning cylinder. As shown in Figure 7B is a cylinder 462, a ring 464 as well as a first end 466A of the microfiber fin and a second end 466B of the microfiber fin. First end 466A and second end 466B represent the two ends of a single microfiber fin. First end 466A is coupled with a connection point (not shown) on ring 464. Second end 466B is coupled with a connection point on another ring (not shown). Figure 7B shows the two ends of the microfiber in a left travel state 468i, a center state 468 ₂ and a right travel state 468 ₃ . In left travel state 468i the microfiber fin has a helix shape along the length of the cleaning cylinder. As can be seen, as ring 464 is rotated in the direction of an arrow 472A (counterclockwise), first end 466A moves in the direction of an arrow 470A closer to second end 466B. In center state 468 ₂ , first end 466A and second end 466B are substantially parallel, meaning that the microfiber fin has a straight, ostensibly rectangular shape, along the cleaning cylinder. As ring 464 is further rotated in the direction of an arrow 472B (also counterclockwise), first end 466A starts to move away from second end 466B, thus resulting in right travel state 468 ₃ , as shown by an arrow 470B. The rotation of first end 466A thus allows the helix shaped of the microfiber fin to be changed such that regardless of the direction of travel of the cleaning cylinder, the helix shaped microfiber fin will always generate a directional air flow which is forward and simultaneously downward the slope of a solar panel surface. According to the disclosed technique, the bidirectional cleaning ability of the cleaning robot, which allows the angle of curvature of the microfiber fins to be changed and adjusted, provides additional value over the prior art. One benefit is that even though the microfiber fins of the disclosed technique clean solar panels without water, the microfiber fins may still become wet, for example after rainfall or because of nighttime dew. In the embodiment of the disclosed technique with an actuator for adjusting the angle of curvature of the microfiber fins, the actuator can be used to rotate the microfiber fins back and forth between a clockwise position and a counter-clockwise position, thus changing the angle of curvature rapidly due to the rotation of the plurality of rings along the central cylinder and affording increased amounts of air to come in contact with the microfiber fins. Such a movement may reduce the amount of time needed to air dry the microfiber fins. In addition, while the cleaning robot is in a docking station, the actuator can be used to position the microfiber fins in a center state, wherein they are straight and not touching one another, to enable faster air drying, as opposed to keeping the microfiber fins in a helix shape while wet, where air drying may take longer due to adjacent microfiber fins touching one another.

Reference is now made to Figure 8, which is a schematic illustration of another waterless solar panel cleaning robot fitted with helix shaped microfiber elements, generally referenced 500, constructed and operative in accordance with a further embodiment of the disclosed technique. Figure 8 schematically shows the cleaning robot of the disclosed technique having at least one helix shaped microfiber fin which enables bidirectional cleaning. As described below, cleaning robot 500 may include a frame or may be constructed as frameless. Cleaning robot 500 is shown from a top view. Cleaning robot 500 includes a cleaning cylinder 502, an upper element 504 and a lower element 506. As mentioned above, at least one of upper element 504 and lower element 506 can include other elements such as a processor, a wireless transceiver, at least one rechargeable power source, a drive motor and a rotation motor (all not shown). Cleaning robot 500 can also include other elements such as guiding sensors (either ultrasonic or optical distance sensors or ultrasonic or optical beam sensors) for ensuring that cleaning robot 500 remains properly aligned as it travels over a solar panel row, an end of row sensor (such as a magnetic sensor) for detecting that cleaning robot 500 has reached the end of the solar panel row, an inertial measurement unit, at least one encoder (for example mounted on the drive motor) for determining a position of cleaning robot 500 over the solar panel row, at least one electronics box for housing electrical components of cleaning robot 500 as well as an emergency kill switch (all not shown). Cleaning robot 500 can also optionally include at least one solar panel unit for self-charging at least one rechargeable power source as well as extension arms (for example as described below in Figures 15-16B), for enabling cleaning robot 500 to cross certain kinds of gaps and spaces between adjacent solar panels (all not shown).

In Figure 8, shown are horizontal wheels 510 and 514 and vertical wheels 508 and 512 which enable cleaning robot 500 to move over the surface of a solar row (not shown). In one embodiment of the disclosed technique, each one of wheels 508 and 512 may be rotated using a separate motor, thus in this embodiment, cleaning robot 500 would have four separate motors for rotating wheels 508 and 512, one motor per wheel. In another embodiment of the disclosed technique, upper element 504 may include only a single motor for rotating wheels 508 whereas lower element 506 may also include only a single motor for rotating wheels 512. Thus in this embodiment, cleaning robot 500 would have two separate motors for rotating wheels 508 and 512. Other numbers of motors are possible for rotating wheels 508 and 512. Cleaning cylinder 502 is coupled between upper element 504 and lower element 506, and is also coupled with a rotation motor (not shown), thus enabling cleaning cylinder 502 to rotate about its central axis. Cleaning cylinder 502 includes an external central cylinder 516 over which are coupled a plurality of rings 518. External central cylinder 516 may be hollow. Two microfiber fins 520 are shown coupled to cleaning cylinder 502 via connection points (not shown) on plurality of rings 518. Cleaning cylinder 502 may optionally include an internal cylinder 522 positioned inside the hollow of external central cylinder 516. Internal cylinder 522 is stationary and does not rotate and couples upper element 504 with lower element 506. Internal cylinder 522 may be coupled with at least one bearing (not shown) to each of upper element 504 and lower element 506 thus affording internal cylinder a degree of flexibility with regards to upper and lower elements 504 and 506 (as described in greater detail below in Figures 10A-10C). External central cylinder 516 is coupled with the rotation motor for rotating central external central cylinder 516 and thus rotating microfiber fins 520. Internal cylinder 522 may be embodied as a support structure for external central cylinder 516. The rotation motor may be coupled directly with central cylinder 516 for direct transmission or indirectly via a transmission belt. A lower ring 524 may have a predetermined amount of relative rotation whereas an upper ring 526 may be fixed, having no amount of relative rotation, thus enabling microfiber fins 520 to switch between two different helix shaped, one suited for clockwise rotation and the other for counter-clockwise rotation, wherein a forward and downward directional air flow is generated based on the helix shape of the microfibers. In one optional embodiment, internal cylinder 522 may also include a plurality of support beams (not shown) for maintaining cleaning cylinder 502 straight and robust and preventing sagging in its middle section.

As internal cylinder 522 is optional, in an embodiment without internal cylinder 522, external central cylinder 516 is coupled directly with the rotation motor for rotating cleaning cylinder 502 and may also be coupled with upper element 504 and lower element 506 via at least one respective bearing. For example, external central cylinder 516 may be coupled with a ball bearing (not shown) to lower element 506 and may be coupled with a gear (not shown) that is coupled with the rotation motor. In this embodiment, the rotation of cleaning cylinder 502 will also cause plurality of rings 518 to rotate. It is noted that in the embodiment of the disclosed technique shown in Figure 8, either with or without internal cylinder 522, due to the absence of a frame over cleaning cylinder 502, cleaning robot 500 may experience vibrations as cleaning cylinder 502 rotates and moves over a solar row. As mentioned above, vibrations in cleaning cylinder 502 are minimized due to the helix shape of the microfiber fins which eliminates any periodicity with regards to contact of the microfiber fins with the solar panel surface. In the case of cleaning cylinder 502 being approximately not longer than 2 meters in length, vibrations experienced in cleaning robot 500 may be negligible, thereby resulting in a cleaning robot which is lighter and includes less parts than an embodiment of the disclosed technique with a frame covering cleaning cylinder 502. The embodiment of Figure 8 affords for a more energy efficient and cost effective cleaning robot for waterlessly cleaning solar panels (i.e., lighter in weight, less complex, fewer parts, lower energy requirements and the like).

According to another embodiment of the disclosed technique, cleaning cylinder 502 may be coupled with two adjustment motors (not shown), each respectively positioned in upper element 504 and lower element 506, for adjusting the height of cleaning cylinder 502 over the solar panel surface (not shown). The adjustment motors may raise cleaning cylinder 502 in order to overcome obstacles on the solar panel, such as when moving from an array of solar panels in a row to a bridge section connecting the array of solar panels to another array of solar panels on the same solar panel row, where there is a significant angular difference between each array of solar panels and the bridge section. The adjustment motors can also lower and raise cleaning cylinder 502 in order to change the amount of pressure the microfiber fins exert on the solar panel surface. For example, if there is heavy soiling on the solar panels, cleaning cylinder 502 may be slightly lowered in order to increase the pressure which the microfiber fins exert on the solar panel surface as they clean the solar panels.

In the case of cleaning cylinder 502 being approximately longer than 2 meters in length (for example 4-6 meters in length or even as long as 10 meters in length), vibrations may be experienced in cleaning robot 500 which are not negligible and according to another embodiment of the disclosed technique, at least one profile (two are shown in Figure 8), shown as profile 528, may optionally be added to cleaning robot 500, thus giving the cleaning robot a frame. Thus even though the disclosed technique has been described in many places as a frameless waterless solar panel cleaning system, according to the disclosed technique, the various cleaning cylinders described above in Figures 2A-8 can be embodied as part of the disclosed technique wherein a frame is added the upper element (such as upper element 504) and the lower element (such as lower element 506) using profiles. The addition of a frame will result in a substantial elimination of vibrations due to the rotation of the cleaning cylinder, even in cleaning robots which are substantially long in length (i.e. , more than 2 meters and up to 6 meters). It is noted that the addition of a frame increases the cost to manufacture and the weight of the cleaning robot, thus increasing its complexity and its energy requirements however eliminating vibrations in cleaning robots of the disclosed technique designed for very tall solar rows (for example, with a height of between 4-10 meters). According to yet another embodiment of the disclosed technique, instead of adding a frame in the case of a very long cleaning cylinder (i.e., more than 2 meters and up to 6 meters in length), at least one wheel can be added to the cleaning cylinder in its middle section to reduce vibrations without the need for a frame. In some embodiments, the aforementioned at least one wheel is not necessary.

According to another embodiment of the disclosed technique, cleaning robot 500 can be constructed with a plurality of straight microfiber fins without a helix shape and without a frame. Even though the helix shape, as explained above, improves the directional airflow for moving soiling both forward and downward, in the case of variable angle solar parks (i.e., solar trackers), where the tilt angle of the solar row at the end of the day when the sun has set may be easily 45° or larger (for example 60°), there is a significant effect of gravity pulling loosened soiling from the solar panel surfaces downward and off the solar panel surfaces. In such a scenario, cleaning robot 500 can be used with straight microfiber fins for loosening and moving soiling forward over the solar panel surfaces as the force of gravity will easily draw loosened soiling downward towards the lower end of the solar row. And as explained below, in another embodiment of the disclosed technique, improved directional airflow, as achieved with helix shaped microfiber fins can also be achieved with straight microfibers. As described above, in the embodiment of the cleaning robot which includes an actuator for changing the angle of curvature of the helix shape, the actuator may be used to position and lock the microfiber fins in a center state and position (see Figures 7A and 7B) when the cleaning robot is used to clean solar trackers. Alternatively, the cleaning robot may be constructed without a helix shaped microfiber fin and without the ability to change the angle of curvature of the helix shape, but simply with a central cylinder and straight microfiber fins. Such an embodiment would not include a frame and could be used to effectively clean solar panels in solar trackers.

According to another aspect of the disclosed technique, the ability to change the angle of curvature of the helix shaped microfiber fins enables the cleaning robot of the disclosed technique to optimize its cleaning based on prevailing wind conditions over the solar park. The cleaning robot of the disclosed technique may be coupled with a weather center providing information about wind conditions in the vicinity of the solar park. Based on the setup of the solar rows in the solar park, a particular cleaning direction (either leftward or rightward over the solar rows) may be preferable to use the direction of the wind advantageously to aid in removing soiling from the solar panel surfaces. Thus according to the disclosed technique, if the prevailing winds over the solar park are strong enough, the effect of the wind might be stronger than the directional airflow generated by the microfiber fins of the cleaning robot and thus the central management unit of the solar park can automatically decide on the most appropriate cleaning direction for the cleaning robot, which can then automatically adjust its helix shape for a given cleaning direction. As an example, the directional airflow of the helix shape of the microfiber fins can generate an airflow equivalent to a wind speed of approximately 10 km/h (kilometers per hour). If the weather forecast for the next day predicts easterly winds stronger than 15 km/h and cleaning robot 500 has finished a cleaning cycle and is located at a western side of a given solar panel row, then at the end of the cleaning cycle, cleaning robot 500 can be given a command to return to an eastern side of the given solar panel row such that the next day, it will clean in the direction of the predicted winds, thereby removing dust, dirt and debris more efficiently. If the predicted winds are in the reverse direction (i.e., westerly) and are predicted as being stronger than 10km/h, at the end of the cleaning cycle, cleaning robot 500 may remain parked and docked at the western side of the given solar panel row so that the day after it will clean by pushing and removing dust, dirt and debris in a westerly direction in line with the predicted westerly wind direction. Reference is now made to Figures 9A-9C, which are schematic illustrations of different solar panel row configurations showing challenges for solar panel cleaning robots, generally referenced 550, 570 and 600 respectively, constructed and operative in accordance with another embodiment of the disclosed technique. With reference to Figure 9A, a row of solar panels 552A-552D is shown. When rows of solar panels are set up and installed, they are usually installed in sections or blocks of solar panels, for example blocks of 4 solar panels, blocks of 8 solar panels, blocks of 16 solar panels and the like. Whereas blocks of solar panels are ideally connected and coupled together to form a monolithic type configuration, imprecisions in the coupling of the solar panels, as well as natural changes in the terrain over which the solar panels are installed, can cause adjacent solar panels to be slightly misaligned. As shown in Figure 9A, solar panel 552B is slightly misaligned with solar panels 552A and 552C, both on its top side, as shown by an arrow 554 and on its bottom side, as shown by an arrow 556.

A typical solar panel cleaning robot which moves horizontally over solar panels 552A-552D in the direction of an arrow 555 will encounter difficulty in remaining aligned and properly coupled with the solar panels as it crosses from solar panel 552A to solar panel 552B and from solar panel 552B to solar panel 552C. The difficulty arises because of the misalignment of the corners of solar panel 552B with the corners of solar panels 552A and 552C. A typical solar panel cleaning robot might get stuck moving from solar panel 552A to 552B and/or might not be able to continue cleaning solar power 552C after cleaning solar panel 552B. It is noted that the misalignment shown in Figure 9A is in a horizontal plane parallel to the plane of solar panels 552A-552D, however the misalignment could also be a vertical plane (not shown). Thus for example, solar panels 552C and 552D may be aligned horizontally however solar panel 552D might be positioned slightly higher in elevation (not shown) than solar panel 552C, thus resulting in a vertical misalignment between adjacent solar panels. As is evident to the worker skilled in the art, solar panels can be simultaneously misaligned both vertically and horizontally, thus making the issue of misalignment even more of a challenge.

With reference to Figure 9B, shown is another solar panel row configuration involving two sections of solar panels, a first section 572A and a second section 572B. Each one of first and second sections 572A and 572B includes a plurality of solar panels 574, arranged side-by-side and also in an upper row and a lower row (not labeled). Plurality of solar panels 574 may also be arranged in a single row (not shown). Each section may include a plurality of solar panels arranged in one or two rows, such as sixteen solar panels, with eight solar panels in an upper row and eight solar panels in a lower row. First and second sections 572A and 572B are separated by a wide gap 576, which can be, for example, anywhere from 20 centimeters in length to ten meters in length. Gaps, such as wide gap 576, are common in solar panel row configurations which can include tens if not hundreds of solar panels, arranged in sections of solar panels as described above.

When horizontal cleaning robots are installed for cleaning solar panels arranged in sections, as shown in Figure 9B, bridge rails may be used to couple adjacent solar panel sections, thereby allowing the cleaning robot to move from solar panel section to solar panel section. As shown, first section 572A is coupled with second section 572B via bridge rails, shown as an upper bridge rail 578A and a lower bridge rail 578B, together forming a bridge over the wide gap. Figure 9B shows an ideal situation wherein upper bridge rail 578A and lower bridge rail 578B appear equal in length, position and angle, thus allowing a cleaning robot, which moves along the upper and lower edges (not labeled) of each section, to easily move from one section to the next, as shown by an arrow 577. However as described below in Figure 90, upper and lower bridge rails are rarely equal in length, position and angle, thus making it more challenging for cleaning robots to easily cross wide gap 576 over the bridge rails without difficulty and without getting stuck and/or even falling off the bridge rails.

With reference to Figure 90, shown is a solar panel row configuration 600 on a terrain 614 having different elevations, shown as a first elevation 6161, a second elevation 6162 and a third elevation 6163. Solar panel row configuration 600 includes two sections of solar panels shown in a row, a first solar panel section 602A and a second solar panel section 602B. First solar panel section 602A is positioned on a plurality of legs 604A and second solar panel section 602B is positioned on a plurality of legs 604B. As shown, some of legs 604A are taller than others and some of legs 604B are also taller than others, thus giving first and second solar panel sections 602A and 602B specific respective angles in relation to terrain 614.

Solar panel row configuration 600 is typical of solar panel rows set up on hilly, mountainous or otherwise rocky terrain, wherein different sections of solar panels may be positioned at different heights and at different angles towards the sky (such as in the case of fixed angle solar panels). As shown, a bridge (not labeled) has been installed for coupling first solar panel section 602A with second solar panel section 602B such that a horizontal cleaning robot can traverse between the solar panel sections. The bridge includes an upper bridge rail 612B and a lower bridge rail 612A. Two dotted lines, 6101 and 610 ₂ , represent a horizontal angle of 0° and are shown to show the difference in angle of each of the solar panel sections. First solar panel section 602A makes an angle 606 with horizontal angle 610i whereas second solar panel section 602B makes an angle 608 with horizontal angle 610 ₂ . As can be seen, angles 606 and 608 are different. Given the difference in angle between angles 606 and 608 as well as the difference in height between legs 604A and 604B, not only are first and second solar panel sections 602A and 602B positioned at different heights and different angles but upper and lower bridge rails 612B and 612A are positioned at different angles relative to one another and are also of different lengths.

The difference in length of upper bridge rail 612B and lower bridge rail 612A, as well as their difference in angle in relation to their respective couplings with first and second solar panel sections 602A and 602B, presents a formidable challenge to cleaning robots which travel horizontally over solar panel row configuration 600 in the direction of an arrow 615 (or in the reverse direction). The change in angle as well as the difference in distance which the lower part of such a cleaning robot must travel as compared to the distance the upper part of such a cleaning robot must travel increases the complexity in design for such a cleaning robot. Overall, the challenge for a horizontal cleaning robot to successfully cross from one solar panel section to another is a formidable one in general for known robotic cleaning solutions. What is thus required is a horizontal cleaning robot capable of crossing a wide gap 617 formed between first and second solar panel sections 602A and 602B while remaining on upper and lower bridge rails 612B and 612A and also capable of transition from the bridge to each of the solar panel sections while remaining coupled with the upper and lower edges (not labeled) of a given solar panel section.

Reference is now made to Figures 10A-10C, which are schematic illustrations of another frameless waterless solar panel cleaning robot having increased flexibility, generally referenced 640, constructed and operative in accordance with a further embodiment of the disclosed technique. Equivalent reference numbers are used in Figures 10A-10C to designate equivalent elements. Frameless waterless solar panel cleaning robot 640 (herein simply cleaning robot 640) is shown in three different views, a perspective view 642A (as shown in Figure 10A), a top view 642B (as shown in Figure 10B) and a side perspective view 642C (as shown in Figure 10C). In general cleaning robot 640 is substantially similar in design to cleaning robots 370 (Figure 6A) and 500 (Figure 8) however cleaning robot 640 has increased flexibility compared to cleaning robots 370 and 500, as described below. With reference to Figure 10A, cleaning robot 640 is shown schematically in perspective view 642A. Cleaning robot 640 includes an upper element 644A, a lower element 644B and a cleaning cylinder 646. A plurality of microfiber elements 648 are coupled with cleaning cylinder 646. Plurality of microfiber elements 648 can have a helix shape as shown above in Figures 6A and 8, however plurality of microfiber elements 648 can also have a straight shape as shown in Figures 10A-10C. In addition, plurality of microfiber elements 648 is shown including three microfiber elements however any number of microfiber elements greater than one can be used. The disclosed technique can also be embodied with the use of a single microfiber element although the efficiency of the cleaning robot might be reduced. The frameless shape of cleaning robot 640 is substantially realized by upper element 644A, lower element 644B and cleaning cylinder 646 which together give cleaning robot 640 an l-shape. The ends of upper element 644A are coupled with wheel couplers 650i and 650 ₂ which are schematically shown whereas the ends of lower element 644B are coupled with wheel couplers 650 ₃ and 650 ₄ which are also schematically shown. Each wheel coupler includes two wheels, a vertical wheel 652 and a horizontal wheel 654. Vertical wheels 652 are used to roll cleaning robot 640 over the surface of a solar panel whereas horizontal wheels 654 roll along the upper and lower side edges of the solar panel, thereby keeping cleaning robot 640 in contact with the solar panel. As described above regarding cleaning robots 370 (Figure 6A) and 500 (Figure 8), the length of cleaning cylinder 646 is substantially the height of a solar panel row such that cleaning robot 640 can travel horizontally over the solar panel row in a straight line.

Unlike the cleaning robots shown above in Figures 6A and 8, cleaning cylinder 646 is coupled with upper and lower elements via respective coupling joints 6681 and 668 ₂ , which each respectively provide independent movement of upper element 644A and lower element 644B in a plurality of directions. Coupling joints 6681 and 668 ₂ provide cleaning cylinder 646 and upper and lower elements 644A and 644B with up to six DOFs, thereby significantly increasing the flexibility of cleaning robot 640. An embodiment of coupling joints 6681 and 668 ₂ is described below in detail in Figures 17. As shown by an arrow 656, coupling joints 6681 and 668 ₂ provide cleaning robot 640 with flexibility in a horizontal plane (not labeled) thus allowing upper element 644A to rotate in the directions of arrow 656. Similar flexibility is provided to lower element 644B however this is not shown by an arrow. As shown by an arrow 658A and an arrow 658B, coupling joints 6681 and 668 ₂ also provide cleaning robot 640 with flexibility in a vertical plane (not labeled) thus allowing lower element 644B to rotate in the directions of arrows 658A and 658B. Similar flexibility is provided to upper element 644A however this is not shown by an arrow. And as shown by an arrow 660, coupling joints 6681 and 6682 together further provide cleaning robot 640 with flexibility in a transverse plane (not labeled) thus allowing cleaning cylinder 646 to rotate in the directions of arrow 660. The horizontal movement as shown by arrow 656 allows one end of upper element 644A to extend beyond the length of cleaning cylinder 646 while allowing the other end of upper element 644A to be within the length of cleaning cylinder 646. The vertical movement as shown by arrows 658A and 658B allows one end of lower element 644B to rotate above the height of cleaning cylinder 646 while allowing the other end of lower element 644B to rotate below the height of cleaning cylinder 646. The transverse movement as shown by arrow 660 allows upper element 644A to be higher in height in a horizontal plane as compared to lower element 644B and vice-versa. Thus as shown in Figure 10A, the configuration of the frameless waterless solar panel cleaning robot of the disclosed technique affords increased flexibility to each of the elements (upper and lower elements 644A and 644B and cleaning cylinder 646) which give cleaning robot 640 it l-shape.

It is noted that each of wheel couplers 650I-650 ₄ may include a separate and independent motor (not shown) for controlling at least one of the respective vertical wheel and horizontal wheel of each wheel coupler. Cleaning robot 640 may also include a wireless transceiver (not shown) for transmitting data about each wheel coupler and for receiving instructions regarding the operation of each motor. As cleaning robot 640 is shown schematically, it may also include other elements such as a processor, guiding sensors (either ultrasonic or optic distance sensors or ultrasonic or optic beam sensors) for ensuring that the cleaning robot remains properly aligned as it travels over a solar panel row, an end of row sensor (such as a magnetic sensor) for detecting that the cleaning robot has reached the end of the solar panel row, at least one angle sensor for measuring the angle formed between the upper element and the lower element with each coupling joint, an inertial measurement unit, at least one encoder (for example mounted on at least one of the motors coupled with the wheel coupler) for determining a position of the cleaning robot over the solar panel row, at least one electronics box for housing electrical components of the cleaning robot as well as an emergency kill switch (all not shown). The cleaning robot can also optionally include at least one solar panel unit for self-charging at least one rechargeable power source as well as extension arms (for example as described below in Figures 15-16B), for enabling the cleaning robot to cross certain kinds of gaps and spaces between adjacent solar panels (all not shown). The cleaning robot can also optionally include a dynamic charging connector in an embodiment where the solar panel unit for self-charging the cleaning robot is positioned on a docking station coupled with the solar panel row and not on the cleaning robot.

Cleaning robot 640 may include at least one flexibility sensor (not shown) to determine the angle and thus the position of at least one of the following main elements, upper element 644A, lower element 644B and/or cleaning cylinder 646, compared to a predefined horizontal, neutral position. The flexibility sensor may be embodied as an encoder, an angle measurement unit, an inertial measurement unit (herein abbreviated IMU) or an accelerometer, for example. A single centralized flexibility sensor may be sufficient for determining the angle of the main elements of the cleaning robot. According to the disclosed technique, the flexibility sensor enables increased detection of the particular position of each main element of cleaning robot 640 as it travels over a solar panel row. Such detection can be particularly useful in improving the maneuvering of cleaning robot 640, especially in a case where cleaning robot 640 may be stuck or unable to move due to one or more of its main elements being flexed too much as compared to the predefined horizontal, neutral position.

It is also noted that cleaning robot 640 as described above provides flexibility in three different planes, a horizontal plane, a vertical plane and a transverse plane, all simultaneously. However according to the disclosed technique, coupling joints 6681 and 6682 may be provided with at least one locking mechanism (not shown) for locking the flexibility of at least one given plane. The locking mechanism may be operated manually and may be used for transportation purposes of the cleaning robot both to and from the solar panel row. The locking mechanism may also be used for limiting the flexibility of the cleaning robot in a particular direction. Thus in one embodiment, cleaning robot 640 may only be flexible in the direction of arrows 656, 658A and 658B but not in the direction of arrow 660. The flexibility afforded to cleaning robot 640 via the locking mechanism may be a function of design and configuration of a particular solar panel array installation. It is further noted that coupling joints 6681 and 6682 may optionally be provided with at least one limiting mechanism (not shown) for limiting the amount of flexibility (for example as measured in degrees) in each plane. Thus for example, the limiting mechanism may enable a user to set the flexibility in the horizontal plane as shown by arrow 656 from between 0° up to 80° degrees in each direction. In another embodiment, the limitation of the flexibility in each plane may be part of the mechanical design and configuration of the cleaning robot. With reference to Figure 10B, shown is the increased flexibility of cleaning robot 640 from a top view, showing the increased flexibility in the horizontal plane. As can be seen, two angles 663i and 663 ₂ are shown, showing the angles formed between upper element 644A and cleaning cylinder 646. The increased flexibility afforded by coupling joint 6681 allows upper element 644A to rotate in the direction of arrow 656, thus enabling angles 663i and 663 ₂ to change, for example, from approximately 45° to 135°, instead of being fixed at 90° which would be the case in cleaning robot 500 (Figure 8), for example. The angles of 663i and 663 ₂ may be changed from 10° to 170°, which can be particularly useful for reducing transportation costs of cleaning robot 640 and for moving cleaning robot 640 from one solar panel row to another solar panel row (either independently or by a transport mechanism). Transportation costs of a product are usually derived from the amount of volume the product occupies on a truck, on a container and/or on a plane. If the upper and lower elements of the cleaning robot can be rotated by around 170°, more cleaning robots can be placed next to one another in a transport (as each cleaning robot will occupy less volume), thereby reducing transportation costs.

Similar flexibility is shown regarding lower element 644B and cleaning cylinder 646 however without reference signs. Two dotted lines 662A and 662B, essentially emerging from vertical wheels 652, show that the increased flexibility in the horizontal plane enable the vertical and horizontal wheels coupled with upper element 644A to be unaligned with the vertical and horizontal wheels coupled with lower element 644B in a first plane (not shown), thus allowing, within limits, upper element 644A to move independently of lower element 644B. As mentioned above, a locking mechanism may be used to lock the flexibility of either upper element 644A, lower element 644B or both.

With reference to Figure 10C, shown is the increased flexibility of cleaning robot 640 from a side perspective view, showing the increased flexibility in the vertical plane. As shown, the increased flexibility afforded by coupling joint 668 ₂ enables lower element 644B to rotate around a vertical plane (not shown) in the direction of arrow 658A. This enables the ends of lower element 644B to rotate above and below a horizontal line 664, instead of being fixed at 0° and in parallel to horizontal line 664, which would be the case in cleaning robot 500 (Figure 8), for example. Horizontal line 664 is merely schematic, and lower element 644B can rotate above and below the plane of a solar panel, at whatever angle it is positioned over the ground. Similar flexibility exists for upper element 644A however this is not shown in Figure 10C. The increased flexibility in the vertical plane enables the vertical and horizontal wheels coupled with upper element 644A to be unaligned with the vertical and horizontal wheels coupled with lower element 644B in a second plane, thus further allowing, within limits, upper element 644A to move independently of lower element 644B. As mentioned above, the ends of lower and upper elements 644B and 644A may be able to rotate up to 80° in each direction around horizontal line 664. In addition, the flexibility as shown in Figure 10C may either be locked or can be limited, as described above. The flexibility as shown in Figures 10B and 10C applies equally to the flexibility in cleaning robot 640 of cleaning cylinder 646, as shown by arrow 660 (Figure 10A), even though this is not fully shown in Figure 10A-10C.

As described below, cleaning robot 640 may include a miter gearbox, enabling the drive motors (not shown) for driving the wheels of the cleaning robot to drive either vertical wheels 652 or horizontal wheels 654. According to the cleaning angle at which a solar row is cleaned by the cleaning robot, the direction of the force (i.e., the weight) placed on each solar panel by cleaning robot 640 relative to the ground (upon which the solar panel is positioned on) can be changed accordingly. For example, if the cleaning angle of the solar row is at 30° degrees, more force might be placed on the solar panel surface as the solar row is more flat than angled. In such an example, the drive motors would drive only vertical wheels 652 so as to provide more grip to the cleaning robot as it moves over the solar row. However if the cleaning angle of the solar row is at 60° degrees, more force might be placed on the solar panel frame as the solar row is more angled than flat. In general, since many solar trackers on the market are designed to have a high stow angle of 50° to 60°, according to the disclosed technique, the cleaning robot can clean solar trackers at their stow angle, and thus solar parks managers do not need to program in an additional cleaning angle besides the preset stow angle of the solar trackers. In this embodiment in case high winds suddenly start, the solar trackers will not be jeopardized since they are already stowed at an optimal angle to cope with sudden winds. In such an example, the drive motors would drive only horizontal wheels 654 so as to provide more grip to the cleaning robot as it moves over the solar row. By providing a drive force to the horizontal wheels, cleaning robot 640 can clean at very high cleaning angles, such as up to 60° degrees. This is also due to the general flexibility afforded to cleaning robot 640 by having a single cleaning cylinder. By having only one beam (cleaning cylinder 646) traverse along the length of a solar panel, the cylinder will have more flexibility in terms of its height and in adjusting to differences in solar panel heights along a solar row as compared to a framed cleaning robot (i.e., a cleaning robot having at least two beams traversing along the length of a solar panel), which will have less flexibility in terms of its height because of the at least two beams which form its frame over the length of a solar panel.

In another embodiment of the disclosed technique, shown in greater detail below in Figure 18, the horizontal wheels of the cleaning robot can be shaped to include a wheel with an extension plate which extends the surface area the horizontal wheels are in contact with vis-a-vis the solar panel. Thus if the cleaning robot cleans the solar panels at a high cleaning angle, such as 60°, the extension plate ensure that the horizontal wheels, especially on the lower element, remain in contact with the solar panel. This increases the stability of the cleaning robot over the solar panel row as it cleans, especially at high cleaning angles and ensures that the cleaning robot remains attached to the solar panels while cleaning. In another embodiment of the disclosed technique, the vertical and horizontal wheels can be replaced with wheels shaped like diablos (i.e., an hourglass shape), where one part of the diablo touches the frame surrounding the solar panel at the side surface of the solar panel, and the other part of the diablo touches the portion of the solar panel frame which is perpendicular to the solar panel surface. In this example, the diablo wheels are positioned at an angle of 45° wherein substantially equal parts of the diablo shape touch the upper surface and side surface of the solar panel. The diablo shape provides a more cost effective configuration in which a wheel coupler set including a vertical wheel and a horizontal wheel can be replaced by a single diablo wheel. Thus for example, a cleaning robot with 8 standard wheels can be replaced by 4 diablo wheels. In another embodiment, the diablo wheels of the cleaning robot can all be positioned horizontally, such that the diablo wheels travel on the outer side surface of the solar panel frame. In this embodiment, the diablo wheels are in contact with the outer frame of the solar panel at its corners, both along the top and bottom parts of the outer frame.

An example embodiment of the frameless waterless solar panel cleaning robot is shown below in Figure 18. As described further below, the weight of various elements of the cleaning robot needs to be properly distributed between the upper element and the lower element so that the cleaning robot is balanced as it travels over a solar panel row. The heaviest components of the cleaning robot include the motor for rotating the cleaning cylinder and the microfiber fins, the gear box coupled with the motor and the cleaning cylinder as well as the rechargeable power source (e.g. a battery). In one embodiment, the motor for rotating the cleaning robot and the gear box may be positioned within upper element whereas the rechargeable power source may be positioned in the lower element. An electronics box containing all the electronic components, for example a processor and a wireless transceiver, may be positioned within the upper element in order to enable the longest wireless signal distance from the cleaning robot to a base station (not shown). Reference is now made to Figures 11 A-11 B, which are schematic illustrations of the frameless waterless solar panel cleaning robot having increased flexibility of Figures 10A-10C used in cleaning the different solar panel row configurations of Figures 9A-9C, generally referenced 700 and 740 respectively, constructed and operative in accordance with another embodiment of the disclosed technique. Equivalent elements in Figures 11 A and 11 B are referenced using equivalent reference signs. With reference to Figure 11 A, shown is a frameless waterless solar panel cleaning robot 706, similar in design to cleaning robot 640 (Figure 10A), including a cleaning cylinder 708, a plurality of microfiber elements 710, an upper element 712A, a lower element 712B, a plurality of vertical wheels 714i and 714 ₂ and a plurality of horizontal wheels 716. Cleaning robot 706 also includes coupling joints and wheels couplers (not labeled), similar to cleaning robot 640.

In Figure 11 A, cleaning robot 706 is used to clean two adjacent solar panels 702A and 702B, in a horizontal direction as shown by an arrow 709. Solar panels 702A and 702B are misaligned horizontally, as shown by an arrow 704. As shown by arrows 718A and 718B, upper element 712A and lower element 712B can rotate in a horizontal plane, thus enabling the vertical wheels of cleaning robot 706 to remain rolling over the surface of the solar panels without the vertical wheels losing contact with the solar panel surface. As shown by two dotted lines 720i and 720 ₂ , lower element 712B can form an angle 722 to match the horizontal misalignment of solar panels 702A and 702B. By rotating lower element 712B in the horizontal plane around the axis shown by arrow 718B, vertical wheels 714 ₁ and 714 ₂ remain in contact with the solar panel surface and can also continue to easily and seamlessly roll over the solar panel surface without getting stuck due to misalignments between adjacent solar panels. The same is true in the reverse direction if cleaning robot 706 was moving in the direction opposite of arrow 709. As upper element 712A moves from solar panel 702B to 702A, cleaning cylinder 708 will be pulled slightly upwards, thus pulling lower element 712B upwards and ensuring that vertical wheels 714 ₁ and 714 ₂ remain in contact with the solar panel surface. The upwards pull of cleaning cylinder 708 will cause lower element 712B to adjust its angle accordingly to easily and seamlessly roll over the solar panel surface without getting stuck due to misalignments between adjacent solar panels. Whereas Figure 11 A shows how the disclosed technique overcomes the challenge of horizontal misalignments between adjacent solar panels, the disclosed technique can equally be used for overcoming the challenge of vertical misalignments between adjacent solar panels as well as horizontal and vertical misalignments between adjacent solar panels.

With reference to Figure 11 B, cleaning robot 706 is shown cleaning adjacent solar panels 742A and 742B in the direction of an arrow 749. As shown, solar panels 742A and 742B are separated by a wide gap 744 and are coupled by a bridge which includes upper bridge rail 746A and lower bridge rail 746B. As shown by arrows 718A and 718B, both upper element 712A and lower element 712B can rotate about a horizontal plane, thus enabling cleaning robot 706 to adjust itself to traverse over the bridge without issue. As shown by dotted lines 748i and 748 ₂ , upper element 712A forms an angle 750 with the upper edge (not labeled) of solar panel 742A, thus enabling its horizontal and vertical wheels to follow the general direction and angle of upper bridge rail 746A. The same is true for lower element 712B however this is shown without reference signs in Figure 11 B. As is clear to the worker skilled in the art, since upper and lower elements 712A and 712B can rotate independently of one another in a horizontal plane, a vertical plane and a transverse plane, cleaning robot 706 can adjust itself to accommodate crossing a bridge even if upper bridge rail 746A and lower bridge rail 746B have different lengths, different heights and different angles between solar panel 742A and solar panel 742B. Since upper element 712A aligns itself to upper bridge rail 746A (due to the force of gravity, the entirety of cleaning robot 706 will be pulled upwards, thus enabling lower element 712B to align itself with lower bridge rail 746B. The horizontal wheels (not labeled) of the cleaning robot restrict the movement of upper element 712A, thus ensuring that the vertical wheels (not labeled) of the cleaning robot remain in contact with either the solar panel surface or the bridge rails. Therefore even if the bridge rails are not parallel to one another due to a misalignment between adjacent solar panels (such as solar panels 742A and 742B), cleaning robot 706 will nonetheless move diagonally over the bridge rails and adjust its upper and lower elements accordingly, due to the flexibility afforded by its coupling joints (not labeled). Thus according to the disclosed technique, a frameless waterless solar panel cleaning robot is described which can meet the challenges of misalignment between solar panels. The cleaning robot of the disclosed technique as described can also cross bridges which couple solar panel row sections together, even if the bridge rails of the bridges are uneven, not parallel and at different angles. Thus cleaning robot 706 could be used to cross the bridge (i.e., upper bridge rail 612B (Figure 9C) and lower bridge rail 612A (Figure 9C)) shown above in Figure 9C. Cleaning robot 706 can be used to cross bridges in solar tracker setups wherein the angle deviation between different sections of a solar panel row in the solar tracker may be quite high and substantial (such as 10°).

With reference back to Figure 10B, the l-shape of upper and lower elements 644A and 644B and cleaning cylinder 646 along with coupling joints 6681 and 668 ₂ can be used not only for increased flexibility of the cleaning robot as it travels over solar panels which may be misaligned with one another, but also for achieving a directional airflow cleaning effect similar to the cleaning effect achieved with helix shaped microfiber elements yet without necessitating cleaning cylinder 646 to have helix shaped microfiber elements. As shown in Figure 10B angle 663 ₂ can be defined as an “angle of attack” of plurality of microfiber elements 648 with respect to a solar panel surface (not shown). If plurality of microfiber elements 648 are mounted in a straight line along the length of cleaning cylinder 646 (as schematically shown in Figure 10B), an increase in the angle of attack (i.e., angle 663 ₂ ) beyond 90° will substantially generate a directional airflow similar to the directional airflow generated by microfiber elements mounted in a helix shape (not shown) around cleaning cylinder 646.

As mentioned above (in Figure 8), each one of upper and lower elements 644A and 644B may include at least one motor for rotating at least one of vertical wheels 652 and/or horizontal wheels 654. By temporarily changing the speed of rotation of one of these motors vis-a-vis the other, upper element 644A can be made to move slightly ahead of lower element 644B (as shown in Figure 10B) as cleaning robot 640 travels over a solar row. Once upper element 644A is ahead of lower element 644B, the speed of both motors (i.e., moving upper and lower elements 644A and 644B) can be made the same, thereby maintaining the slanted l-shape of cleaning robot 640. As shown, cleaning cylinder 646 has an angle of attack and will substantially generate the same downward airflow effect as achieved by a cleaning cylinder having microfiber elements wrapped around it in a helix shape. Thus the slanted or tilted l-shape as shown in Figure 10B can be used to achieve the Archimedean screw cleaning effect of helix shaped microfiber elements without necessitating helix shaped microfiber elements.

Different angles of attack can be set depending on the relative speeds of the motors moving the wheels of upper and lower elements 644A and 644B. Different angles of attack may be chosen depending on various factors relating to the type of solar row to be cleaned as well as the kind of soiling and/or dirt or debris which is to be removed from the solar panel surfaces. For example, a higher angle of attack of 20° (i.e., angle 663 ₂ would be set to 110°) may be needed to remove snow from solar panel surfaces whereas a lower angle of attack of 10° (i.e., angle 663 ₂ would be set to 100°) may be sufficient for removing dust and debris from solar panel surfaces. As another example, the angle of the solar row with respect to the ground may also determine an appropriate angle of attack. As the angle of the solar row with the respect to the ground becomes steeper, a lower angle of attack should be sufficient for effectively removing dirt, dust and debris down the solar panel using the directional airflow of the disclosed technique. As mentioned above, the slanted l-shape of cleaning robot 640 as shown in Figure 10B enables microfiber elements to be positioned straight along the length of cleaning cylinder 646 (as shown in Figure 10B) thereby making the design, construction and manufacturing of cleaning cylinder 646 with microfiber elements easier and more cost-effective than a cleaning cylinder with helix-shaped microfiber elements, while nonetheless achieving the same directional airflow effect of the Archimedean screw shape achieved by helix-shaped microfiber elements.

Reference is now made to Figures 12A-12B, which are schematic illustrations of a first embodiment of a beam sensor for use with a waterless solar panel cleaning robot shown in a side view and a top view, generally referenced 770 and 772 respectively, constructed and operative in accordance with a further embodiment of the disclosed technique. Equivalent elements in Figures 12A-12B are referenced using equivalent reference numbers. As described above in Figures 6A, 8 and 10A-10C, the disclosed technique relates to a frameless waterless solar panel cleaning robot which generally moves horizontally over a solar panel row. Especially in the case of the cleaning robot of Figures 10A-10C which includes increased flexibility, there is a need to monitor the position of the horizontal and vertical wheels of the cleaning robot to ensure that the wheels of the cleaning robot remain in contact with the solar panel and that the cleaning robot substantially remains aligned with the solar panel row as is travels over and cleans the solar panels. Figures 12A-12B represent a first embodiment of the disclosed technique for monitoring the position of the horizontal and vertical wheels using a beam sensor. It is noted that even though the description below in in Figures 12A-13B relates to a frameless waterless solar panel cleaning robot, the use of beam sensors as described below can apply equally as well to a framed waterless solar panel cleaning robot (as described above in Figure 8 as profile 528) according to the disclosed technique, wherein beam sensors can be used to protect such a framed cleaning robot from falling off a solar panel surface, thus protecting both the cleaning robot and the solar panels from damage, and also providing the cleaning robot with a guidance method for travelling over the solar panels row. With reference to Figure 12A, shown is a portion of a cleaning robot (similar in construction to any of the described cleaning robots herein) travelling over a solar panel 782. The cleaning robot (not labeled) includes a wheel coupler 790 to which a vertical wheel 786 and a horizontal wheel 788 are coupled with. As shown, both vertical wheel 786 and horizontal wheel 788 are in contact with solar panel 782, vertical wheel 786 being in contact with the top surface of solar panel 782 and horizontal wheel 788 being in contact with an edge surface of solar panel 782. A C-shaped bracket 792 is coupled with wheel coupler 790 (shown in better detail below in Figure 12B) and includes a lower end 794i, an upper end 794 ₂ and a curved portion 796. In the first embodiment shown in Figure 12A (and also in Figures 12B and 12E below), curved portion 796 is situated closer to lower end 794 _{1 ;} giving bracket 792 its C-shape. Lower end 794 ₁ includes a first beam unit 798A and upper end 794 ₂ includes a second beam unit 798B thus forming a beam sensor (not labeled). One of beam units 798A and 798B acts as a transmitter for transmitting a light beam while the other beam unit acts as a receiver for receiving the transmitted light beam. As shown, beam units 798A and 798B face one another such that a light beam 800 can be transmitted from one beam unit to the other. Beam units 798A and 798B can be any light beam unit capable of either transmitting and/or receiving light beams, wherein the light can be visible light, infrared light, ultraviolet light or any other beam of light within the electromagnetic spectrum. In some embodiments, beam units 798A and 798B are infrared light beam units which can transmit light beam 800 as an infrared light beam. Infrared light beams (as well as most light beams outside the visible spectrum) have the advantage of being impervious to inclement weather conditions that can include rain, fog, snow, dust, dirt, sand and the like, thus being able to be transmitted and received regardless of the weather conditions on the solar panel.

With reference to Figure 12B, the cleaning robot with its beam sensor is shown from a top view. A second solar panel 784 is now visible as is an arm 802 for coupling C-shaped bracket 792 with wheel coupler 790. As can be seen, a gap 804 exists between adjacent solar panels 802 and 804. Arm 802 may be positioned at a predetermined distance in front of vertical wheel 786 such that a prediction can be made as to when C-shaped bracket 792 should be in line with gap 804 such that light beam 800 travels between beam units 798A and 798B.

The beam sensor of the disclosed technique works as follows. The beam sensor is considered active when light beam 800 forms a straight line from one of the beam units to the other. As an example, first beam unit 798A will be considered a transmitter of light beam 800 and second beam unit 798B will be considered a receiver of light beam 800. Transmitter 798A is constantly sending light beam 800 to receiver 798B. However as shown, the beam sensor should only be active when C-shaped bracket 792 (i.e. , the beam sensor including the beam units) passes gap 804. Thus as shown in both Figures 12A and 12B, light beam 800 travels from transmitter 798A to receiver 798B. However as vertical wheel 786 and horizontal wheel 788 travel over solar panels 782 and 784, provided both vertical wheel 786 and horizontal wheel 788 are in contact respectively with the top surface and edge surface of the solar panel, the beam sensor will not be active and light beam 800 will not be received by receiver 798B (not shown in Figures 12A and 12B) even though transmitter 798A nonetheless constantly transmits light beam 800. This is due to the curvature and angle at which beam units 798A and 798B are positioned. The angle and curvature of the beam units are set such that the solar panel surface will cause light beam 800 to be blocked provided both vertical wheel 786 and horizontal wheel 788 are both in contact with the solar panel. Said otherwise, the inactivity of the beam sensor ensures that the cleaning robot is travelling substantially in a straight line.

In addition, since vertical wheel 786 and horizontal wheel 788 both include encoders (not shown) for respectively counting the turns of each wheel, and considering the dimensions of each wheel are known as are the dimensions of solar panels 782 and 784, as well as the size of gap 804 and the length of arm 802, a prediction can be made as to when and for how long the beam sensor should be inactive and when the beam sensor should be active. As explained above, the beam sensor should only be active when the cleaning robot is crossing gap 804. As described in further detail below in Figures 13A and 13B, activity in the beam sensor when C-shaped bracket 792 is not positioned over gap 804 is an indication that the cleaning robot is veering off course and that horizontal wheel 788 or both vertical wheel 786 and horizontal wheel 788 are not positioned properly on the solar panel surface. The beam sensor of the disclosed technique may be coupled with a wireless transceiver (not shown) positioned in wheel coupler 790, for transmitting and receiving signals relating to the activity and inactivity of the beam sensor. The beam sensor of the disclosed technique may alternatively be coupled via a wired connection to a processor (not shown) in the cleaning robot for sending and receiving signals relating to the activity and inactivity of the beam sensor.

The beam sensor of the disclosed technique as described herein thus enables the position of the cleaning robot to be determined and controlled. According to the disclosed technique, since the cleaning robot as described above includes four wheel couplers, a beam sensor as described herein (including C-shaped bracket 792 and first and second beam units 798A and 798B) can be included and coupled with each wheel coupler, therefore the cleaning robot would have four beam sensors, one for each set of vertical and horizontal wheels. The cleaning robot could then also have four separate transceivers (not shown), one per wheel coupler, or a centralized transceiver (not shown) which is coupled with each wheel coupler. And as an example, arm 802 may be approximately 10 centimeters in length. Since each corner of the cleaning robot is equipped with a beam sensor, the precise position of each end of the upper and lower elements of the cleaning robot (such as upper element 644A and lower element 644B in Figures 10A-10C) can be monitored and controlled. For example, if the beam sensor at the bottom right corner of the cleaning robot (i.e., right side of the lower element) becomes active while the cleaning robot is travelling over the solar panels at a position when the beam sensor should be inactive, this is an indication that at least one of the wheels coupled with the wheel coupler at the bottom right corner of the cleaning robot is either not in contact with the solar panel or is close to not being in contact with the solar panel. As each wheel coupler may include a separate motor, the motor of each wheel coupler may turn at a different speed to reposition the bottom right corner of the cleaning robot such that its vertical and horizontal wheels are back in contact with the solar panel surface. For example, the motor at the bottom right hand corner might rotate its respective wheel coupler faster in order to have the vertical and horizontal wheels in that corner realigned with the solar panel frame, thus causing the cleaning robot to climb back onto the solar panel surface where it can clean the solar panel surface more efficiently. Even though the cleaning robot of the disclosed technique has mostly been described as having a drive motor for each wheel coupler, the disclosed technique can be embodied as having a single drive motor for the wheel couplers in the upper element and another single drive motor for the wheel couplers in the lower element. In this embodiment, a chain or drive belt (not shown) may be needed to enable a single motor to drive more than one wheel coupler. In this embodiment, a miter gearbox (not shown) can also be used to enable a single drive motor to drive more than one wheel coupler. In another embodiment of the disclosed technique, a single drive motor can be used to drive all the wheel couplers of the cleaning robot. In this embodiment, at least two chains or drive belts are required to drive the wheel couplers in each of the upper and lower elements as well as a rotating rod coupled with the single drive motor and coupled between the two chains or drive belts to drive them both. The chains or drive belts can also be coupled between the upper and lower wheel couplers. According to another embodiment of the disclosed technique, the cleaning robot may include only two beam sensors, for example two on either the upper end or lower end of the cleaning robot. In addition, other numbers of beam sensors are possible as well besides two or four. For example, eight beam sensors may be used either for redundancy purposes and/or for improved precision in detection and monitoring of the position of the horizontal and vertical wheels on the solar panel surface. It is also noted that the C-shape of bracket 792 making up the beam sensor is not meant to be taken as limiting and that bracket 792 may have other shapes for keeping first and second beam units 798A and 798B aligned with one another. Any shape of bracket 792 can be used provided first and second beam units 798A and 798B are kept in a straight line. It is further noted that as shown, C-shaped bracket 792 shows light beam 800 travelling in a diagonal direction from one beam unit to another. However according to the disclosed technique, the bracket can be angled and positioned such that the first and second beam units are positioned perpendicularly to the surface of solar panel 782. In such a configuration, first beam unit 798A would be positioned under solar panel 782 (not shown) whereas second beam unit 798B would be positioned over solar panel 782 (also not shown), such that the intersection of the light beam would be with a portion of the solar panel surface. For example, the beam units could be positioned such that light beam 800 intersects the solar panel surface within approximately 10-20 millimeters from the edge of solar panel 782.

According to another embodiment of the disclosed technique (not shown), first and second beam units 798A and 798B can be replaced by a single ultrasonic sensor for measuring the distance of the cleaning robot from the solar panel surface or frame. In this embodiment, a different configuration than shown in Figures 12A and 12B would be used to mount the ultrasonic sensor and a predetermined distance measurement value would be set to determine when the cleaning robot is considered to be veering off course and not travelling over the solar panel in a straight direction. In another embodiment of the disclosed technique, first and second beam units 798A and 798B can be replaced by a single infrared sensor for measuring distance of the cleaning robot from the solar panel frame or surface. In a further embodiment of the disclosed technique, the first and second beam units can be replaced with a single inductive sensor for detecting the presence of a magnetic field. Thus when the cleaning robot is moving over a solar panel, the inductive sensor will detect a disturbance in the magnetic field due to the presence of the metal frame housing the solar panel, and as the cleaning robot moves from solar panel to solar panel, the inductive sensor will temporarily not detect any disturbance to the magnetic field at the space between adjacent solar panels, thus being able to determine that the cleaning robot is moving from one solar panel to the next. In another embodiment of the disclosed technique, first and second beam units can be embodied as ultrasound beam units instead of infrared beam units, wherein one beam sensor transmits an ultrasound signal and another beam sensor receives the ultrasound signal.

It is noted that in Figures 12A-13B, the beam sensors are positioned 180° apart, held together by a C-shape bracket, substantially facing one another. In another embodiment of the disclosed technique (not shown), the beam sensors can be positioned 90° apart, thus being at an angle of 45° from the solar panel surface and the solar panel frame. In this embodiment, each beam sensor substantially receives a reflection from the solar panel surface while the cleaning robot traverses over the solar panels. In this embodiment, the C-shaped bracket would be replaced by a smaller L-shaped bracket installed above the solar panel, thus eliminating the protrusion of the C-shaped bracket below the solar panel, and allowing for better navigability of the cleaning robot. When crossing a gap, such as gap 804, no reflections will be received and thus the beam sensors can determine that the cleaning robot is crossing a gap between adjacent solar panels.

It is further noted that in Figures 12A-13B, the beam sensors are shown as being positioned at the edges of the cleaning robot, however other positions of the beams sensors are possible. In addition, the beam sensors are shown positioned in a C-shape, however it is clear to the worker skilled in the art that other geometries regarding the positions of the beam sensors are possible and are a design choice within the knowledge of the worker skilled in the art.

Reference is now made to Figures 12C-12D, which are schematic illustrations of a second embodiment of a beam sensor for use with a waterless solar panel cleaning robot shown in a side view and a top view, generally referenced 774 and 776, constructed and operative in accordance with another embodiment of the disclosed technique. Equivalent elements in Figures 12A-12D are referenced using equivalent reference numbers. With reference to Figure 12C, a beam sensor similar to the beam sensor shown in Figures 12A-12B is shown, including a C-shaped bracket 792’ having a lower end 794 ₁ and an upper end 794 ₂ to which a first beam unit 798A and a second beam unit 798B are respectively coupled with. The main difference shown in Figure 12C is the position of a curved portion 796’ of C-shaped bracket 792’. As compared to C-shaped bracket 792 in Figure 12A, C-shaped bracket 792’ in Figure 12C has curved portion 796’ located on the upper side of C-shaped bracket 792’, closer to upper end 794 ₂ . In all other respects, the beam sensor of Figure 12C is equivalent to the beam sensor of Figure 12A. C-shaped bracket 792’ has more the shape of a miniscule 'r' as opposed to the more pronounced capital ‘C’ shape of C-shaped bracket 792.

With reference to Figure 12D, due to the positioning of C-shaped bracket 792’, only second beam unit 798B is visible from the top view as shown. In addition, there is no significant change in the positioning or coupling of C-shaped bracket 792’ to arm 802 which couples the beam sensor to wheel coupler 790. It is noted that the use of the beam sensor configuration of Figures 12A-12B versus the beam sensor configuration of Figures 12C-12D may be a design consideration regarding the particular design of the solar panel row the cleaning robot is used on. The beam sensor configuration of Figures 12A-12B avoids having any portion of the beam sensor being over the upper surface of the solar panels whereas the beam sensor configuration of Figures 12C-12D avoids having any portion of the beam sensor being under the lower surface of the solar panels. For example, if support beams or structures are used to hold up a solar panel row and are positioned at the edges of each solar panel, then the beam sensor configuration of Figures 12C-12D might be more suitable as first beam unit 798A would not interfere with any of the support beams or structures, which might be the case if the beam sensor configuration of Figures 12A-12B was used.

Reference is now made to Figures 12E-12F, which are schematic illustrations of the first and second embodiments of the beam sensors of Figures 12A-12D shown in a perspective view, generally referenced 778 and 780, constructed and operative in accordance with a further embodiment of the disclosed technique. Equivalent elements in Figures 12A-12F are referenced using equivalent reference numbers. Figure 12E shows the beam sensor of Figures 12A-12B in a perspective view whereas Figure 12F shows the beam sensor of Figure 12C-12D in a perspective view. The angle and curvature of C-shaped brackets 792 and 792’ are clearly shown as well as the transmission and reception of light beam 800 from first beam unit 798A to second beam unit 798B through gap 804.

In general, the beam sensor of the disclosed technique provides the following functions. Since each wheel coupler is equipped with its own beam sensor, if the travel direction of the cleaning robot over the solar panels begins to shift, then the beam sensor can be used to identify if a particular vertical and horizontal wheel set will get stuck and/or possibly lose contact with the solar panel row. In addition, since solar panel rows are positioned with a gap between adjacent solar panels and each wheel coupler may include at least one encoder, the beam sensor of the disclosed technique can be used to determine an accurate position of the cleaning robot over a solar panel row. For example, each time the beam sensor becomes active when passing a gap, such as gap 804, an indication can be registered that the cleaning robot has travelled past a single solar panel. Thus the number of times the beam sensor is active can indicate how many solar panels have been traversed by the cleaning robot. It is noted that in some embodiments of the disclosed technique, encoders may not be included in each wheel coupler. In such an embodiment, a centralized IMU (not shown) in the cleaning robot can be used. Thus using the beam sensors, the centralized IMU and time measurements of the activity and inactivity of the beam sensors, the position of the cleaning robot over a solar panel row can be determined and monitored. Eliminating the use of encoders can be considered if the manufacturing cost of the cleaning robot is to be reduced.

The beam sensors of the disclosed technique can also be used to control the speed of the cleaning robot, certainly as it approaches a gap between adjacent solar panels. Since an arm is used to couple the beam sensor to the wheel coupler and the arm positions the beam sensor in front of the cleaning robot, activation of the beam sensor can be used to indicate to the cleaning robot that it is approaching a gap and that the speed of the cleaning robot should be adjusted accordingly. In addition, since the cleaning robot in some embodiments includes four beam sensors, the beam sensors can be used to separately adjust the speed of each side and each end of the cleaning robot, especially when a gap crossing between adjacent solar panels is identified. For example, if a gap larger than 10 cm (which is merely an example) is detected, then this may be considered a gap which requires the cleaning robot to slow down so as to soften the fall of the horizontal and vertical wheels onto the gap, thereby reducing the risk of damage to the solar panels. In this example, the processor of the cleaning robot may instruct the drive motors to drive the vertical and horizontal wheels at half speed when the start of a gap is detected, even before the wheels proximate to the gap reach the gap. Once the back wheels of the cleaning robot have passed the gap, the drive motors can be instructed to speed up the movement of the cleaning robot. The beam sensors described above are positioned in front of the wheels of the cleaning robot and thus can detect that the cleaning robot has entered a large gap even before the front wheels of the cleaning robot reach the gap. As the distance between a pair of beam sensors mounted on the upper and lower elements on the same side of the cleaning robot is known, the time between each one of them detecting a gap can be used to determine the speed of the upper and/or lower elements of the cleaning robot by using encoders which may be positioned within the drive motors of the wheels. The determined speed can then be used to adjust the speed of each of the upper and lower elements as the cleaning robot moves onto the gap.

In another embodiment of the disclosed technique, the beam sensors (together with a map (described below) of the solar panel row stored in a memory or processor of the cleaning robot) can also be used to slow down the revolutions per minute (herein abbreviated RPM) of the cleaning cylinder as it approaches the end or beginning of a solar panel array to prevent the microfiber fins from getting stuck as they either leave or enter a solar panel array for cleaning. The slowing down of the RPM of the cleaning cylinder can by coordinated and in sync with reduction in speed of the drive motors.

The beam sensors of the disclosed technique can also be used to prevent possible damage to the cleaning robot and/or solar panels during a cleaning run. Since the size of gap 804 is known, a prediction can be made as to how long each beam sensor should be active as the cleaning robot crosses gap 804. The beam sensors can thus be used to identify a missing solar panel in a solar panel row and thus prevent the cleaning robot from falling off the solar panel row. In the case of crossing a bridge between adjacent solar panel sections, the beam sensors can be used to detect and identify a disconnected bridge rail and thus prevent the cleaning robot from falling off the bridge. Furthermore, the amount of time a sensor beam is active in conjunction with the counting of the encoders positioned in each wheel coupler can be used to sense that the cleaning robot is entering or exiting a bridge as well as entering or exiting a docking station. This might be identified by a specific pattern of sensor beam activity and/or inactivity given the construction of the bridge and the docking station. Also, the beam sensors can be used to determine if the cleaning robot is stuck, for example if one of the vertical and/or horizontal wheels is turning however there is no forward movement of the cleaning robot. This can be determined by the beam sensors as there is an expected time at which the beam sensors are expected to be active as the cleaning robot passes gaps between adjacent solar panels. The lack of beam sensor activity can thus be used to indicate that the cleaning robot is indeed stuck and not moving forward or backward over the solar panel row surface.

It is noted that the disclosed technique provides for a robust installation of the beam sensors, enabling the beam sensors to be firmly coupled with wheel couplers of the cleaning robot. The robustness can also be expressed by the use of two pairs of beam sensors, on each side of the upper element and each side of the lower element of the cleaning robot, thus equipping the cleaning robot with at least four beam sensors in total. The use of at least four beam sensors enables some redundancy between the information which the beam sensors can derive and can thus be used to validate the data derived from the beam sensors. The plurality of beam sensors can also be used to validate the encoders positioned in the drive motors and can be used as a backup control for controlling the drive motors in case the encoders malfunction. In addition, the distance between pairs of beam units is small enough (approximately 30 centimeters for example) such that sensor tolerance is high. It is noted that in the embodiment in which the beam units are embodied as infrared beam units, gaps between adjacent solar panels as small as 3 millimeters can be identified by activity of the beam sensors. The beam sensor configuration of the disclosed technique also provides a cost effective solution for sensing the position of a cleaning robot on a solar panel surface by significantly reducing the bill of materials cost (on the order of tens of US dollars) per beam sensor, as infrared beam units are significantly less expensive than alternative sensor units, such as industrial grade ultrasonic sensors.

It is also noted that at the entry and/or exit of a docking station (not shown) for the cleaning robot of the disclosed technique, a brushing element can be positioned around the position of the beam sensors used for the cleaning robot. As the cleaning robot moves past the brushing element, the brushing element will clean the distal end of the beams sensors of any dirt, dust and/or debris which might have accumulated there on, in order to maintain optimal beam sensor performance.

Reference is now made to Figures 13A-13B, which are schematic illustrations of the first and second embodiments of the beam sensors of Figures 12A-12B shown in a side view showing misalignment detection of the wheels of the cleaning robot and the solar panel, generally referenced 830 and 832, constructed and operative in accordance with another embodiment of the disclosed technique. With reference to Figure 13A, shown is a portion of a cleaning robot 831 cleaning a solar panel 838. Cleaning robot 831 is similar to the cleaning robots shown above in Figures 6A, 8 and 10A-10C and includes the beam sensor of Figure 12A. Cleaning robot 831 includes a vertical wheel 834 and a horizontal wheel 836. In Figure 13A, vertical wheel 834 and horizontal wheel 836 are shown as being misaligned with solar panel 838, thus there is a portion 840 of vertical wheel 834 which is not in contact with solar panel 838 and a gap 844 now exists between the edge surface of solar panel 838 and horizontal wheel 836. Due to the presence of gap 844 and that portion 840 is not in contact with the solar panel surface, a light beam 842 will travel from the transmitter beam unit (not labeled) to the receiver beam unit (not labeled) even if the beam units are not positioned over a gap between adjacent solar panels. Thus light beam 842 will be constantly transmitted and received as cleaning robot 831 travels over solar panel 838 due to the misalignment of both vertical wheel 834 and horizontal wheel 836. As explained above, such an indication by the beam sensor can be used by a central processor (not shown) of the cleaning robot to adjust the speed of vertical wheel 834 and horizontal wheel 836 and/or the speed of the other vertical and horizontal wheel pairs (not shown) of cleaning robot 831 to reduce the size of portion 840 and to eliminate gap 844 such that horizontal wheel 836 is once again in contact with the edge surface of solar panel 838.

With reference to Figure 13B, a similar misalignment between the vertical and horizontal wheels is shown however with the beam sensor having the configuration of the beam sensor shown in Figure 12B above. As can be seen also in this configuration, if there is a portion of vertical wheel 834, shown as portion 840, not in contact with the solar panel surface and there is also a gap between horizontal wheel 836 and the edge surface of solar panel 838, shown as gap 844, light beam 842 will be constantly transmitted and received thus indicating that there is a misalignment between the cleaning robot and solar panel 838.

Reference is now made to Figures 14A-14B, which are schematic illustrations of a solar panel row including a large gap and bridge, generally referenced 860 and 880 respectively, constructed and operative in accordance with a further embodiment of the disclosed technique. Equivalent elements in Figures 14A and 14B are referenced using equivalent reference numbers. With reference to Figure 14A, shown is solar panel row 860 including a plurality of solar panels 862A-862I. Solar panels 862A-862C form a first section of solar panels (not labeled), solar panels 862D-862F form a second section of solar panels (not labeled) and solar panels 862G-862I form a third section of solar panels (not labeled). As can be seen, a gap 864 exists between the first and second sections of solar panels whereas a gap 866 exists between the second and third sections of solar panels. Gap 866 is sufficiently large and occurs infrequently along the length of a solar panel row such that it warrants a bridge to couple the two sections, shown by an upper bridge rail 868A and a lower bridge rail 868B, for a horizontal cleaning robot. However gap 864 is not sufficiently large to warrant a bridge section. A solar panel row may include a plurality of gaps the size of gap 864 such that the cost of closing such gaps with bridges in a single solar panel row is high and not economical. Whereas the setup and configuration of plurality of solar panels 862A-862I is not necessarily typical, setups as shown in Figure 14A do exist, wherein certain sections of solar panels may be separated by a relatively small gap (such as one meter) whereas other sections of solar panels may be separated by a relatively large gap (such as 5-10 meters). The installation of a cleaning robot which travels horizontally over plurality of solar panels 862A-862I necessitates the installation of bridges between adjacent sections of solar panels. However a large solar panel row (for example, including hundreds of solar panels) may include tens of gaps the size of gap 864 yet only a few gaps the size of gap 866. Thus a solar park owner may be prepared to invest in the installation of bridges to couple solar panel sections separated by gaps the size of gap 866 in order to install a horizontal cleaning robot however may not be prepared to invest in installing tens of bridges to couple solar panel sections separated by gaps the size of gap 864.

With reference to Figure 14B, solar panel row 880 is shown with a cleaning robot 882 over plurality of solar panels 862A-862I shown at three different positions: a first position 884A, a second position 884B and a third position 884C. Cleaning robot 882 is substantially similar to the cleaning robots shown above in Figures 6A, 8 and 10A-10C. For the purposes of explanation, cleaning robot 882 is only shown including an upper element 886A, a lower element 886B, a cleaning cylinder 888 coupling upper element 886A with lower element 886B and a plurality of vertical wheels 890 with a respective plurality of horizontal wheels 892 (shown using dotted lines), however cleaning robot 882 also includes a plurality of microfiber elements (not shown), a wireless transceiver (not shown), wheel couplers (not shown) and the like, as explained above. Cleaning robot 882 may also include adjustment motors (not shown), for adjusting the height of cleaning cylinder 888, for example, when the cleaning robot passes over a gap between adjacent solar panel sections coupled together by a bridge section, such as wide gap 617 (Figure 9C).

As shown in first position 884A, the wheels of a right side 894A of upper element 886A and the wheels of a right side 894B of lower element 886B can easily cross the small gap (not labeled) between solar panels 862A and 862B. As shown in second position 884B, the wheels of right side 894A and right 894B will not be able to cross gap 864 and cleaning robot 882 will fall off of solar panel 862C as gap 864 is larger than the diameter of the horizontal and vertical wheels even though gap 864 is smaller than the width of upper and lower elements 886A and 886B. As shown in third position 884C, the wheels of right side 894A and right side 894B will be able to cross gap 866 between solar panels 862F and 862G, due to the presence of upper bridge rail 868A and lower bridge rail 868B, which travel over the bridge as shown in Figure 14B. As can be seen from Figure 14B, cleaning robot 882 can easily cross small gaps between adjacent solar panels within a solar panel section and can also easily cross gaps between adjacent solar panel sections coupled with a bridge. However cleaning robot 882 as shown lacks an ability to cross large gaps between solar panel sections which are not large enough, or occur too frequently in a solar panel row, to necessarily warrant or financially justify the installation of a bridge however which are larger than the diameter of the wheels of cleaning robot 882.

Reference is now made to Figure 15, which is a schematic illustration of a frameless waterless solar panel cleaning robot capable of crossing the large gap of Figure 14B, generally referenced 920, constructed and operative in accordance with another embodiment of the disclosed technique. Cleaning robot 920 is substantially similar in design to the cleaning robots shown above in Figures 6A, 8 and 10A-10C and includes an upper element 922A, a lower element 922B and a cleaning cylinder 924 to which microfiber elements (not shown) are coupled with. Cleaning robot 920 also includes a plurality of vertical wheels 926 as well as a plurality of horizontal wheels 928. As shown, cleaning cylinder 924 extends beyond upper and lower elements 922A and 922B and is coupled with an arms extension section 930A proximate to upper element 922A and an arms extension section 930B proximate to lower element 922B. Another embodiment of arms extension sections 930A and 930B is shown below in greater detail in Figure 19. Arms extension sections 930A and 930B are identical however one is placed at the upper end of cleaning cylinder 924 whereas the other is placed at the lower end of cleaning cylinder 924. Hence only arms extension section 930A will be explained herein. As shown, cleaning cylinder 924 is coupled with a housing 932, which in turn is coupled with extension arms 934 ₁ and 934 ₂ . The distal ends of extension arms 934 ₁ and 934 ₂ are respectively coupled with large horizontal wheels 936i and 936 ₂ . A plurality of arrows 938 shows that extension arms 934i and 934 ₂ can be rotated along a horizontal plane (not shown) and substantially moved up and down. Housing 932 may include a motor (not shown) and/or other mechanism, such as a pulley mechanism (not shown) for moving the extension arms in the directions of plurality of arrows 938. In general, arms extension sections 930A and 930B have two main positions for the extension arms, an engaged position (as shown in solid lines) and a disengaged position (as shown in dotted lines, silhouetted). Thus extension arms 934 ₁ and 934 ₂ are shown in the engaged position whereas extension arms 940i and 940 ₂ are shown in the disengaged position. In the engaged position, extension arms 934 ₁ and 934 ₂ are at angle such that large horizontal wheels 936i and 936 ₂ are almost in contact with the edge surface of a solar panel while cleaning robot 920 moves along the edge surface of a solar panel. When the wheels of cleaning robot 920 cross a large gap, large horizontal wheels 936i and 936 ₂ may briefly be in contact with the edge surface of two adjacent solar panels. In the disengaged position, extension arms 934 ₁ and 934 ₂ are at an angle such that large horizontal wheels 936i and 936 ₂ are not in contact with the edge surface of a solar panel at all. In the engaged position, large horizontal wheels 936i and 936 ₂ are functionally similar to training wheels on bicycles and only come into contact with the edge surface of a solar panel when either one of plurality of vertical wheels 926 and/or plurality of horizontal wheels 928 momentarily loses contact with the edge surface of a solar panel as the cleaning robot crosses over a large gap between adjacent solar panels.

The length of extension arms 934 ₁ and 934 ₂ is such that when in the engaged position, their combined length is greater than the width of a large gap, such as gap 864 (Figure 14A), separating two sections of solar panels. Thus when in the engaged position, arms extension sections 930A and 930B can be used to enable the cleaning robot to traverse over a large gap between adjacent solar panels when no bridge is installed between the adjacent solar panels. Thus for example, if gap 864 (Figure 14B) is around 15 cm and the diameter of plurality of vertical wheels 926 and/or plurality of horizontal wheels 928 is around 14 cm, the wheels of cleaning robot 920 will fall into the gap, resulting in cleaning robot 920 getting stuck and also potentially causing damage to the solar panels adjacent to the gap, if cleaning robot 920 is not equipped with arms extension sections 930A and 930B. Thus in this example, for arms extension sections 930A and 930B to aid cleaning robot 920 in successfully passing over the gap without getting stuck, the distance between each of large horizontal wheels 936i and 936 ₂ and the wheels of cleaning robot 920 (either plurality of vertical wheels 926 and/or plurality of horizontal wheels 928) must be more than 15 cm. It is noted that cleaning robot 920 may also include beam sensors (not shown) as described above in Figures 12A-12F as well as coupling joints (not shown) as described above in Figures 10A-10C and as described below in Figure 17.

It is further noted that as shown, the disengaged position has extension arms 934 ₁ and 934 ₂ in a horizontal position. This is merely schematic, as in the disengaged position, extension arms 934 ₁ and 934 ₂ may be rotated even further away from the edge surface of a solar panel, for example as much as 45°-70° from the disengaged position they are currently shown in in Figure 15. For example, if the cleaning robot is to park over a gap between solar panels where a bridge section is situated, such as gap 866 (Figure 14A), a parking disengaged position may be used wherein extension arms 934 ₁ and 934 ₂ can be rotated as high as 90° to minimize the profile of the cleaning robot and therefore minimize any shadowing caused by the cleaning robot during the day. The minimal profile of the cleaning robot can also be used if the cleaning robot parks and docks at a docking station located at an end of a solar row. Minimizing the profile of the cleaning robot while parking and docking enables positioning the solar panel for recharging the rechargeable power source of the cleaning robot in the docking station itself instead of on the cleaning robot. Such a positioning of this solar panel minimizes the weight of the cleaning robot while nonetheless locating this solar panel for recharging very close to the cleaning cylinder of the cleaning robot. This in turn provides for a narrower docking station structure. A narrow docking station minimizes the necessary room required for a docking station, thereby allowing for more ground area for the installation of solar panels, thus optimizing the utilization of the ground for solar power production. In another embodiment of the disclosed technique, the bridge rails over a gap may include parking elements (such as humps, slots or indentations) which the cleaning robot can pass when travelling over the bridge rails. The humps, slots or indentations may be placed such that when extension arms 93^ and 934 ₂ are lowered into the engaged position, large horizontal wheels 936i and 936 ₂ will be positioned in the parking elements. Thus each bridge rail which is to act as a parking station for the cleaning robot may include at least four parking elements such that the large horizontal wheels of the cleaning robot can be used together with the parking elements for locking the position of the cleaning robot so it will not move during the day, even in the presence of winds. An example of such parking elements is described below in greater detail in Figure 20. It is also noted that in one embodiment, large horizontal wheels 936i and 936 ₂ are motorized and can be rotated via a motor (not shown) whereas in another embodiment large horizontal wheels 936i and 936 ₂ are not motorized and effectively function as support (i.e., training) wheels for cleaning robot 920. For example, a single motor may suffice for moving the large horizontal wheels 936i and 936 ₂ on the upper element and another single motor may suffice for moving the large horizontal wheels (not labeled) on the lower element. In another embodiment, each large horizontal wheel may be moved using a dedicated motor.

In another embodiment of the disclosed technique, extension arms 934 ₁ and 934 ₂ are not coupled with housing 932 and may be coupled with opposite ends of upper element 922A, for example as shown below in Figure 19. In this embodiment, each one of extension arms 934 ₁ and 934 ₂ can be operated separately and may be coupled with a separate motor for independent movement of each extension arm between the engaged and disengaged positions. In the embodiment of the disclosed technique as shown, extension arms 934 ₁ and 934 ₂ are shown as rotating between the engaged and disengaged positions. However in a further embodiment, extension arms 934 ₁ and 934 ₂ may alternate between the engaged and disengaged position by an eccentric movement, by a collapsing movement, by a folding movement and the like, as described below in Figure 19.

Reference is now made to Figures 16A-16B, which are schematic illustrations of a solar panel row including a large gap and bridge showing the cleaning robot of Figure 15 crossing both the large gap and the bridge, generally referenced 960 and 962 respectively, constructed and operative in accordance with a further embodiment of the disclosed technique. Equivalent elements in Figures 16A and 16B are referenced using equivalent reference numbers. With reference to Figure 16A, shown is a plurality of solar panels 964A-964J arranged in a row. Plurality of solar panels 964A-964F form a first solar panel section and plurality of solar panels 964G-964J form a second solar panel section. The two solar panel sections are separated by a large gap 973, having a width shown by an arrow 974. A cleaning robot 966, substantially similar to cleaning robot 920 (Figure 15), is shown at three different positions over plurality of solar panels 964A-964J, a first position 968A, a second position 968B and a third position 968C. As shown cleaning robot 966 includes a plurality of arms extension sections 970 on both its upper end (not labeled) and lower end (not labeled).

As shown in first position 968A, plurality of arms extension sections 970 are kept in an engaged position while cleaning robot 966 travels of the plurality of solar panels. As can be seen, the wheels of each arms extension section are slightly above the edge surface of the plurality of solar panels, shown schematically by an arrow 971. As cleaning robot 966 approaches large gap 973, plurality of arms extension sections 970 remain in the engaged position. As can be seen in second position 968B, when actually crossing large gap 973, the wheels (not labeled) of the right side of plurality of arms extension sections 970 (shown by an arrow 975A) are in contact with the edge surface of the solar panels whereas the wheels (not labeled) of the left side of plurality of arms extension sections 970 (shown by an arrow 975B) are barely in contact with the edge surface of the solar panels. The combined length of extension arms 972 is greater than width 974 of large gap 973 such that as the right end of the vertical wheels (not labeled) of cleaning robot 966 near the end of solar panel 964F, the right end wheels (not labeled) of plurality of arms extension sections 970 are already in contact with the adjacent solar panel, which is solar panel 964G. Plurality of arms extension sections 970 remain in the engaged position even after cleaning robot 966 has fully traversed large gap 973. As shown, this occurs for the arms extension section at both the upper and lower ends of cleaning robot 966. As shown in third position 968C, arms extension sections 970 remain in the engaged position, although as shown, like in first position 968A, the wheels of arms extension sections 970 are not in direct contact with the edge surface of the solar panels.

In general, the position of large gap 973 is known in relation to the number of solar panels in a given solar panel row, thus in one embodiment, encoders (not shown) in the horizontal and vertical wheels of the cleaning robot can be used to determine when cleaning robot 966 is approaching a large gap such as large gap 973 and a command can then be given to put plurality of arms extension sections 970 into the engaged position in case plurality of arms extension sections 970 are not already in the engaged position. In another embodiment, the use of beam sensors, as described above in Figures 12A-13B, can be used to determine the position of large gap 973 without the use of encoders. A similar command can then be given to keep them in the engaged position or to put them into the disengaged position when the encoders and/or beam sensors have determined that cleaning robot 966 has passed over large gap 973. In general, in the engaged position, extension arms 972 may not actually touch the solar panels while cleaning robot 966 passes over adjacent solar panels such as plurality of solar panels 964A-964F. Extension arms 972 will only touch the solar panels when cleaning robot 966 passes over a gap (similar to how training wheels on a bicycle do not actually touch the ground unless the rider is not properly balanced). Thus in one embodiment of the disclosed technique, extension arms 972 can always be engaged and will only be put into the disengaged position when cleaning robot 966 approaches a large gap which is coupled via a bridge and bridge rails. In another embodiment of the disclosed technique, activation and deactivation of a plurality of beam sensors (not shown) can be used to determine when plurality of arms extension sections 970 should be put into the engaged position and correspondingly, when they should be returned back to the disengaged position, if required. It is noted that when cleaning robot 966 is traversing over a large gap 973, a command may be given to plurality of arms extension sections 970 to remain fixed at the angle defining the engaged position, in order to prevent the wheels of plurality of arms extension sections 970 from falling into large gap 973 and preventing cleaning robot 966 from advancing over large gap 973.

With reference to Figure 16B, cleaning robot 966 is again shown in three positions however the solar panel row now has a much larger gap 976 that warranted a bridge to couple between solar panel 964F and solar panel 964G via an upper bridge rail 978A and a lower bridge rail 978B. As can be seen, plurality of arms extension sections 970 remain in the engaged position through first and third positions 968A and 968C, similar to what was shown in Figure 16A. As seen, the wheels of the arms extension sections in the engaged position barely touch the edge surface of the solar panels. However when crossing over upper bridge rail 978A and lower bridge rail 978B, as shown in second position 968B, plurality of arms extension sections 970 are put into the disengaged position to prevent the arms extension section from interfering with the crossing of cleaning robot 966 over the bridge. In general, according to the disclosed technique, the overall width of cleaning robot 966 should be brought to a minimum when cleaning robot 966 crosses over a bridge. In one embodiment of the disclosed technique, this is achieved by putting plurality of arms extension sections 970 into the disengaged position wherein plurality of arms extension sections 970 may be rotated upwards to an angle of 70° on each side (not shown). Plurality of arms extension sections 970 are not required while cleaning robot 966 crosses upper bridge rail 978A and lower bridge rail 978B as the bridge itself allows the cleaning robot to cross from solar panel 964F to solar panel 964G. In addition, plurality of arms extension sections 970 may interfere with either one of upper bridge rail 978A and lower bridge rail 978B if kept in the engaged position while crossing the bridge. Thus plurality of arms extension sections 970 are put into the disengaged position when traversing a bridge as upper bridge rail 978A and lower bridge rail 978B may have different lengths, angles and heights, as described above in Figure 9C. Thus keeping plurality of arms extension sections 970 in the engaged position (not shown), especially over a bridge section, might actually interfere with the crossing of cleaning robot 966 over the bridge section, especially at the entrance onto and the exit from upper and lower bridge rails 978A and 978B. As mentioned above, since the position of bridges on a solar panel row are known, either by using encoders and/or beam sensors, cleaning robot 966 can be commanded appropriately as it approaches a gap between adjacent solar panels as to whether it should disengage its plurality of arms extension sections 970 or whether plurality of arms extension sections 970 should remain in the engaged position.

According to another embodiment of the disclosed technique, even if cleaning robot 966 does not know exactly where it is located on a solar panel row, if cleaning robot 966 becomes stuck and cannot advance or reverse, then movement of plurality of arms extension sections 970 can be effected, either from the engaged position to the disengaged position or vice-versa, in an attempt to release cleaning robot 966 from the position it finds itself in if indeed plurality of arms extension sections 970 are the cause of cleaning robot 966 being stuck. Lowering the arms extension sections in the case of the cleaning robot being stuck may also be used to free a vertical and/or horizontal wheel which became stuck. Lowering the arms extension section sufficiently can slightly lift a portion of the cleaning robot, thus enhancing its ability to free a wheel which has become stuck.

According to a further embodiment of the disclosed technique, the frameless waterless solar panel cleaning robot as described herein, for example in Figures 5A, 6A, 8, 10A-10C, 12A-13B and 15, can be docked on a solar panel row, for example in the middle of a solar panel row over a bridge section, without having to return the cleaning robot to an end of the solar panel row specifically for docking. In this embodiment, the cleaning robot can even dock on a solar panel since the profile of the cleaning robot is substantially slim (for example approximately 150 millimeters in width when the microfiber elements are not rotated) and thus lightweight. This enables the possibility of docking the cleaning robot in the middle of a solar panel row, either over a bridge or over a large gap (as described above in 9C and Figure 14A-16B), thus saving on the energy costs of returning a cleaning robot to the end of a solar panel row for docking and also providing a stronger support structure for docking the cleaning robot, as the middle of a solar panel row construction is usually more stable than the ends. Docking the cleaning robot over a solar panel or adjacent to a solar panel allows the cleaning robot to rotate with the solar panel in the case of a solar panel row which is variable in angle (i.e., a solar tracker), thus enabling the cleaning robot to be equipped with a smaller self-charging panel as the cleaning robot will maximize its sun exposure during daylight hours. In either case (whether on a bridge, at the end of a solar panel row or adjacent to a solar panel in the middle of a solar panel row), a dedicated locking mechanism may be used to ensure that the cleaning robot remains locked and parked and will not move, even in the presence of strong winds. An example of a locking mechanism for the cleaning robot positioned over a bridge is described below in Figure 20. Another advantage of docking the cleaning robot in the middle of a solar panel row is that such a docking obviates the need for the cleaning robot to cross an obstacle which may be present between the solar panel row and a docking station located at an end of the solar panel row. The obstacle may be present due to changes in the terrain below the docking station and the end of the solar panel row. A further advantage is that a cost effective auxiliary docking position is provided for the cleaning robot in case there is an issue with a docking station located at the end of a solar panel row and the cleaning robot cannot dock there and/or in the case of inclement weather where it is quicker for the cleaning robot to dock at a nearby docking station in the middle of a solar row and not have to travel to the end of a solar row which may be kilometers long. According to a further embodiment of the disclosed technique, the solar panel cleaning robot as described herein, for example in Figures 5A, 6A, 8, 10A-10C, 12A-13B and 15, which includes microfiber fins shaped in the form of a helix, can be cleaned of excess dirt and debris absorbed in the microfiber fins after a cleaning cycle, by moving the cleaning robot back and forth at the end of a solar row or over an open space (similar to cleaning a rug). In another embodiment, a cleaning element can be added to at least one end of a solar row, which is positioned slightly below the height of the microfiber fins. The cleaning element may be a profile which is the length of a microfiber fin and may optionally include a brush or bristles positioned along the profile in the direction of the microfiber fins. Given the height of the cleaning element, as the microfiber fins pass the cleaning element, they will come into contact with the cleaning element. The friction between the microfiber fins and the cleaning element will substantially remove any excess dirt or debris in the microfiber fins.

According to another embodiment of the disclosed technique, the solar panel cleaning robot as described herein, for example in Figures 5A, 6A, 8, 10A-10C, 12A-13B and 15, can be constructed such that the cleaning cylinder with microfiber fins can be easily removed (for example with a quick lock system) and replaced with other cleaning cylinders having different attachments. For example, the microfiber fins cleaning cylinder can be replaced with a cleaning cylinder having nylon brushes. For another example, the microfiber fins cleaning cylinder can be replaced with a cleaning cylinder having wipers for using the natural dew present on the solar panels in the early morning hours to aid in cleaning the solar panels of excess soiling due to dust and debris mixing with liquids on the solar panel surface such as dew. As a further example, the microfiber fins cleaning cylinder can be replaced with a cleaning cylinder having thicker or thinner microfiber fins depending on the type of dirt and/or debris to be removed from the solar panel surfaces (e.g., dust, snow, bird soiling and the like).

According to another embodiment of the disclosed technique, due to the ability of the cleaning robot to clean in either direction over a solar row, as described above, especially in Figures 5A, 6A, 8, 10A-10C, 12A-13B and 15, a method is provided wherein the cleaning robot can increase its cleaning efficiency by cleaning a solar row at different cleaning angles. Since a solar tracker can move for example from -60° to +60° over the course of a single day, the cleaning angle of the solar row can be set to be -40° on a given day and then set to be +40° the next day. Such a method of cleaning according to the disclosed technique can significantly increase the cleaning efficiency of the cleaning robot, since the lower part of a solar panel is where more dirt and dust accumulates over time. By swapping (for example every other day) which portion of a solar panel is the upper portion and which is the lower portion, the solar row will be cleaned more effectively. According to the disclosed technique, such a method will also not add any additional wear and tear to the solar tracker system as the solar panels have to return to the eastern side every night to be ready for the sun in the morning. As an example, on a given night, after the solar panels have moved east to west, while the solar panels are still facing west, the cleaning robot can be sent out to the solar panels and once cleaning is complete, the solar panels can be given an instruction to rotate and return to the east side in time for sunrise. On the next night, the solar panels might be instructed to first rotate back to the east and then the cleaning robot would be sent out to clean. Thus on one night, one side of the solar panels will be considered the lower side having more accumulated debris and dust whereas on a subsequent night, the other side of the solar panels will be considered the lower side having more accumulated debris and dust.

According to another embodiment of the disclosed technique, a map of the misalignments of the solar panels in a solar panel row and in the solar park in general, can be generated. As described above, the cleaning robot can be equipped with beam sensors, which can be used along with encoders (and optionally a GPS), to determine the position of the cleaning robot over a solar panel row and in general in the solar park. The cleaning robot may also be equipped with at least one centralized IMU and optionally at least one accelerometer. Thus as the cleaning robot traverses over a solar panel row for the first time, according to the disclosed technique, a map of all the steps, misalignments and other challenges for the cleaning robot in the solar park can be generated. Each time the centralized IMU and/or accelerometer records a value of the angle of at least one of the elements of the cleaning robot which is beyond a predetermined limit, the position of the cleaning robot can be stored based on the beam sensors and encoders, marked as a position on the solar panel row where there is a potential misalignment issue. Each subsequent pass of the cleaning robot over the same solar panel row can then make use of the map, which can be used by the cleaning robot for either slowing down or speeding up its drive motor in an appropriate manner to overcome the stored challenge that a particular position over the solar panel row might pose to the cleaning robot.

Reference is now made to Figure 17 which shows schematic illustrations of the coupling joint of the frameless waterless solar panel cleaning robot having increased flexibility of Figures 10A-10C, generally referenced 1000, constructed and operative in accordance with another embodiment of the disclosed technique. It is noted that Figure 17 is merely schematic and represents an example of the coupling joints of the cleaning robot of the disclosed technique, showing its increased flexibility. Other designs and configurations are possible and within the scope of the knowledge of the worker skilled in the art. In the example shown in Figure 17, an upper coupling joint is shown in views 1002A and 1002B whereas a lower coupling joint is shown in views 1002C, 1002D, 1002E and 1002F. The upper coupling joint is positioned in the upper element of the cleaning robot whereas the lower coupling joint is positioned in the lower element of the cleaning robot.

In view 1002A, a cleaning cylinder 1004 is shown along with an upper element, shown in a first position 1006A and a second position 1006B (which is a rotated position). Cleaning cylinder 1004 may be coupled with a gearbox (shown but not labeled in view 1002B) for rotating the external cylinder (not shown) to which microfiber fins (also not shown) are coupled to. As can be seen, a pin 1008 is coupled with a plate 1010. Pin 1008 goes all the way through the upper element, more clearly seen in view 1002B. Plate 1010 is coupled with cleaning cylinder 1004 in a joint that enables rotating. As shown in view 1002B, plate 1010 may be coupled with the gearbox to which the cleaning cylinder is coupled with. The movement of pin 1008 and plate 1010 enables the upper element rotation in the direction shown by an arrow 1007, which can be defined as the yaw axis of the cleaning robot. In another embodiment, pin 1008 may be embodied without plate 1010 and can be coupled with the gearbox by a bearing. As described below briefly, a similar structure is present in the lower element to enable the same kind of rotation.

In a view 1002C, cleaning cylinder 1004 is shown coupled with a lower element that is also shown in a first position 1012A and a second position 1012B (which is a rotated position). A pin 1014 is shown coupled with a plate 1016, similar to the pin and plate shown in views 1002A and 1002B. In the lower element, cleaning cylinder 1004 may be coupled with a tilt adaptor 1018. Similar to the gearbox shown in view 1002B, tilt adaptor 1018 has a housing for plate 1016 and with pin 1014 extending through the lower element, the lower element can rotate in the direction of an arrow 1009, also giving the lower element rotation in the yaw axis of the cleaning robot. This is clearly shown in a view 1002D.

In a view 1002E, the roll axis of the cleaning robot is shown. Cleaning cylinder 1004 is coupled with tilt adaptor 1018. As per embodiments described above, cleaning cylinder 1004 may be the internal cylinder which is stationary and upon which the external cylinder (not shown) is placed which rotates the microfiber elements (not shown). As seen in view 1002E, second position 1012B, which is the rotated position, is now shown rotating in the direction of an arrow 1011 and not in the direction of arrow 1009. As is evident to the worker skilled in the art, cleaning cylinder 1004 can rotate in the directions of arrows 1007, 1009 and 1011 simultaneously. Tilt adaptor 1018 has a pin 1020 enabling it to rotate in the direction of arrow 1011. As shown in a view 1002F, plate 1016 is coupled with tilt adaptor 1018 such that it moves and rotates with tilt adaptor 1018 while nonetheless enabling plate 1016 to rotate. Due to the length of cleaning cylinder 1004 (which may be 2-6 meters if not even longer), a pitch direction of rotation (not shown) along the length of cleaning cylinder 1004 is also possible.

Reference is now made to Figure 18 which is a schematic illustration of a further frameless waterless solar panel cleaning robot having increased flexibility, generally referenced 1030, constructed and operative in accordance with a further embodiment of the disclosed technique. Figure 18 shows an example design of a cleaning robot 1032. Shown is a cleaning cylinder 1034 to which a plurality of microfiber fins 1036 is coupled with, the microfiber fins having a helix shape. Cleaning cylinder 1034 is coupled with an upper element 1038 and a lower element 1040. As can be seen, both the upper and lower elements include a plurality of vertical wheels 1042 and a plurality of horizontal wheels 1044. Upper element 1038 may house certain components of cleaning robot 1032, such as a gearbox and a rotation motor (both not labeled) for rotating cleaning cylinder 1034, schematically shown as elements 1046, whereas lower element 1040 may house other components of the cleaning robot such as a rechargeable power source and a processor (both not labeled), schematically shown as elements 1048. Each set of a horizontal wheel and vertical wheel, referred to above as a wheel coupler, may include a dedicated drive motor (not shown) for driving the horizontal wheel, the vertical wheel or both.

Shown in Figure 18 also are two embodiments of the vertical and horizontal wheels for cleaning robot 1032. In a first embodiment, shown in a view 1050A, and similar to what is shown in cleaning robot 1032, plurality of horizontal wheels 1044 can be embodied as a wheel with an extension plate (which can also be described as a wheel with a conical extension), generally referenced as a horizontal wheel 1052. A vertical wheel 1066 however remains as a basic wheel without an extension plate. Horizontal wheel 1052 includes a wheel portion 1054 and an extension portion 1056. Horizontal wheel 1052 is a monolithic structure. Extension portion 1056 extends out from wheel portion 1054, thus increasing the surface area and range of surface contact of horizontal wheel 1052 with a solar panel 1060. As shown by an arrow 1058, extension portion 1056 is positioned and extends under a lower surface of solar panel 1060, thereby increasing the grip of the cleaning robot with the solar panel. As described above, in the case of a high cleaning angle, such as 60°, extension portion 1056 aids in keeping the vertical wheels of upper element 1038 in close proximity to solar panel 1060 and prevents the upper portion in general of cleaning robot 1032 from detaching from the solar panel which would occur if horizontal wheel 1054 diverted too much from the solar panel.

As described above, both the horizontal and vertical wheels in a wheel coupler can be replaced with a single wheel having a diablo shape, as shown in a second embodiment of the wheel coupler shown in a view 1050B. A diablo shaped wheel is shown with an upper portion 1062B and a lower portion 1062A. The hourglass shape of the wheel in view 1050B includes an indentation 1064 which is where the corner of a solar panel is positioned. Upper portion 1062B is functionally similar to vertical wheel 1066 in view 1050A whereas lower portion 1062A is functionally similar to horizontal wheel 1052 in view 1050A. The wheel in view 1050B thus also enables the cleaning robot to remain substantially coupled with and traversing over a solar panel while cleaning, even at high cleaning angles.

Reference is now made to Figure 19 which is a schematic illustration of another frameless waterless solar panel cleaning robot capable of crossing the large gap of Figure 14B, generally referenced 1080, constructed and operative in accordance with another embodiment of the disclosed technique. A lower portion 1082 of the cleaning robot (not fully shown) is shown in Figure 19, as an example. Lower portion 1082 includes horizontal wheels 1084 and vertical wheels 1086. Shown as well are extension portions 1087A and 1087B. Unlike the embodiment of the extension portions shown in Figure 15, extension portions 1087A and 1087B do not extend from the center of the lower and upper elements (i.e., from the cleaning cylinder, as shown in Figure 15) but rather extend from the end of each side of lower portion 1082. Extension portions 1087A and 1087B represent two different embodiments shown in a single illustration. Thus in a cleaning robot constructed according to the disclosed technique with extension portions, all the extension portions would either be embodied as extension portion 1087A or extension portion 1087B.

Extension portion 1087A includes a wheel with an extension plate (or a conical extension) 1088 as well as an arm 1092 which can move between an engaged position and a disengaged position. Wheel 1088 is substantially similar in design to horizontal wheel 1052 (Figure 18) and may differ in the length of the extension plate (or the size and angle of the conical extension) as well as in the width and/or diameter of the wheel portion (not labeled). Extension portion 1087B includes a diablo shaped wheel 1090 as well as arm 1092 and is similar in design to the wheel shown in view 1050B (Figure 18). As mentioned above, extension portions 1087A and/or 1087B are used to enable the cleaning robot to pass over gaps between adjacent solar panels which may be larger than the width of either the upper and/or lower elements of the cleaning robot but which are not large enough to warrant a bridge section to couple the adjacent solar panels together.

Shown in Figure 19 as well is arm 1092 in two different positions, a disengaged position 1100A and an engaged position 1100B. In disengaged position 1100A, an arm 1102 can be seen coupled with a folding gear mechanism 1104. The wheel (not shown) is coupled with an opening 1106 in arm 1102. In engaged position 1100B, folding gear mechanism 1104 has moved to another position which has moved arm 1102 such that is it now in the engaged position. The folding gear mechanism shown is merely an example and other gears and mechanisms can be used to position arm 1102 such that the wheel attached to it at opening 1106 is either proximate to (but not necessarily touching) a solar panel surface (i.e., the engaged position) or at a distance from the solar panel surface (i.e., the disengaged position).

Reference is now made to Figure 20 which is a schematic illustration of a locking mechanism for a cleaning robot positioned over a bridge, generally referenced 1120, constructed and operative in accordance with a further embodiment of the disclosed technique. As shown, a locking mechanism 1122 can be positioned around a profile 1124, which can be a bridge rail connecting two adjacent solar panels (not shown) and forming a gap between the solar panels. Locking mechanism 1122 includes a body 1126, which can be made from plastic as well as a plurality of bumpers 1128, which can be made from a soft material such as rubber or silicon. As shown, plurality of bumpers 1128 can be positioned on the top and side portions of body 1126. Locking mechanism 1122 can also include at least one lower bumper 1130.

A first view 1132A shows a portion of a cleaning robot (not labeled) docking in locking mechanism 1122. As shown, plurality of bumpers 1128 positioned on the top of locking mechanism 1122 is positioned to tightly fit around a plurality of vertical wheels 1134. In a second view 1132B, shown from a back side and an underside, it can be seen how a wheel portion of a horizontal wheel 1136 also snugly fits into plurality of bumpers 1128 which are placed on the side of locking mechanism 1122. An extension portion of horizontal wheel 1136 is also shown as making contact with lower bumper 1130. Locking mechanism 1122 represents an example design of a locking mechanism for enabling the cleaning robot to dock and park in the middle of a solar panel row. When traversing over a solar panel row, the drive motors of the cleaning robot are strong enough to enable both the vertical and horizontal wheels of the cleaning robot to pass over plurality of bumpers 1128. However when the cleaning robot is to park in locking mechanism 1122, as shown, once plurality of vertical and horizontal wheels 1134 and 1136 enter the space between two bumpers and their respective drive motors are turned off, the material of plurality of bumpers 1128 (such as silicon or rubber) provides sufficient friction to prevent the cleaning robot from exiting locking mechanism 1122 on its own, for example if strong winds pass over the solar panel row. The addition of lower bumper 1130 provides additional friction for maintaining the cleaning robot in locking mechanism 1122 and preventing the cleaning robot from being lifted by strong winds and detaching from the bridge in an upwards motion.

A plurality of locking mechanisms 1122 can be positioned along at least some of the gaps in a solar panel row. Since gaps in the solar panel row are coupled, according to the disclosed technique, with bridge rails, the locking mechanisms are placed in a strong and sturdy position over the solar panel row, which may be strong and more stable that docking and parking stations placed at the end of a solar panel row. In addition, a gap where a locking mechanism is placed can also include at least one solar panel for recharging the rechargeable power source of the cleaning robot. In such an embodiment, the locking mechanism may be equipped with an electrical contact coupled with the aforementioned at least one solar panel. When the cleaning robot enters the locking mechanism and docks and parks there, its rechargeable power source is coupled with the at least one solar panel for recharging it during daylight hours.

Reference is now made to Figures 21A-21 B which are schematic illustrations of other embodiments of the cleaning cylinder of the frameless waterless solar panel cleaning robot showing the coupling of the microfiber fins, generally referenced 1160 and 1190 respectively, constructed and operative in accordance with another embodiment of the disclosed technique. With reference to Figure 21 A, a plurality of rings and spacers are shown, similar to what was described above in Figure 7A. A first image shows a single ring 1162 including six fasteners 1164. Other numbers of fasteners are possible and are dependent on the number of microfiber fins to be coupled with ring 1162. A second image shows a spacer 1166, which is substantially a hollow cylinder which can be placed around a central cylinder (not shown in the second image). A third image shows how a plurality of rings 1162 can be coupled with a plurality of microfiber fins 1168 via fasteners 1164 of the rings. As can be seen, a microfiber fin is inserted into a fastener of each ring. The orientation of each ring vis-a-vis an adjacent can give plurality of microfiber fins 1168 a straight shape or a helix shape of varying curvature. A fourth image, labeled 1170, shows how the plurality of rings coupled with the microfiber fins can be fitted over a central cylinder 1172, which may be the external cylinder which is rotated around. As shown, plurality of rings 1162 couple plurality of microfiber fins 1168. Between each ring, a spacer 1166 is positioned, thus ensuring that each ring of plurality of rings 1162 remains spaced apart from an adjacent ring. Plurality of rings 1162 may be able to either freely rotate around central cylinder 1172 or may be limited in rotation. For example, one of the rings may be fixed such that it cannot rotate independently of central cylinder 1172 whereas the other rings may be able to rotate independently. Depending on the direction of rotation of central cylinder 1172 in such an example, plurality of microfiber fins 1168 will form a helix shape having a particular direction. The angle of the helix shape will thus be a function of the length of each spacer 1166 as well as the distance between the fasteners of adjacent ones of plurality of rings 1162. In one embodiment, the microfiber fins can be fabricated as long fins such as shown on Figure 21 A which span the length of central cylinder 1172. In another embodiment, the microfiber fins can be fabricated as a plurality of short microfiber sections coupled with fasteners 1164, wherein an overlap of a few millimeters is created between adjacent microfiber fins, in order to maintain the continuity of the helix shape of the microfiber fins while also not leaving any areas of the solar panel surface which are uncleaned.

With reference to Figure 21 B, another embodiment for coupling the microfiber fins to the central cylinder is shown. In a first image, a ring structure 1192 is shown, made from three identical curved elements 1194A, 1194B and 1194C. As can be seen curved elements 1194A-1194C are interlocking and together form a cylindrical shape. Each one of curved elements 1194A-1194C also includes a hole 1196, positioned in the center of each curved element. Shown as well is a button 1198, which includes a base 1200 and a clip 1202. Button 1198 is designed to fit and snap into hole 1196. As can be seen, a portion 1204 of a microfiber fin can be gripped by button 1198 and a microfiber fin 1206 can be gripped by a plurality of buttons 1198. Ring structure 1192 with a plurality of buttons 1198 inserted into holes 1196 is shown while being positioned around a central cylinder 1208. In this embodiment, ring structure 1192 serves the dual purpose of rings 1162 and spacers 1166 (both in Figure 21 A) by enabling a microfiber fin to be coupled with a central cylinder while also keeping the connection points spaced apart. A plurality of ring structures 1192 can be coupled with one another (not shown) along the length of central cylinder 1208. As the position of each ring structure can be adjusted, the position of holes 1196 enables a plurality of microfiber fins to have a helix shape. In another embodiment, ring structure 1192 can be fabricated as a monolithic element without the locking mechanism shown to interlock curved elements 1194A-1194C in Figure 21 B.

It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow.